Heat And Mass Transfer

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Heat Transfer Refrigeration And Air Conditioning SECTION-01 1. The wet bulb temperature during sensible heating of air A. remains constant B. increases C. decreases Answer: Option B 2. The C.O.P. of an absorption type refrigerator is given by (where T1 = Temperature at which the working substance receives heat, T2 = Temperature of cooling water, and T3 = Evaporator temperature) B. Please refer www.indiabix.com Answer: Option B 3. Which of the following statement is wrong? C. The thermal conductivity of solid metals increases with rise in temperature, Answer: Option C 4. In free convection heat transfer transition from laminar to turbulent flow is governed by the critical value of the D. Prandtl number, Grashoff's number Answer: Option D 5. In a refrigerating machine, heat rejected is __________ heat absorbed. A. equal to B. less than C. greater than Answer: Option C 6. The humidity ratio or specific humidity is the mass of water vapour present in D. 1 kg of dry air Answer: Option D 7. The formation of frost on cooling coils in a refrigerator C. increases power consumption Answer: Option C 8. The by-pass factor for a cooling coil A. increases with increase in velocity of air passing through it Answer: Option A 9. The difference between dry bulb temperature and wet bulb temperature, is called B. wet bulb depression Answer: Option B 10. Defrosting of a refrigerator may be done by stopping the compressor for a short period. A. Correct Answer: Option A 11. According to Dalton's law of partial pressures, (where pb = Barometric pressure, pa = Partial pressure of dry air, and pv = Partial pressure of water vapour) B. Pb = pa + pv (Please refer www.indiabix.com) Answer: Option B 12. The heat transfer by conduction through a thick sphere is given by B. (Please refer www.indiabix.com) Answer: Option B 13. The relative humidity is defined as D. the ratio of actual mass of water vapour in a given volume of moist air to the mass of water vapour in the same volume of saturated air at the same temperature and pressure Answer: Option D 14. Fourier's law of heat conduction is (where Q = Amount of heat flow through the body in unit time, A = Surface area of heat flow, taken at right angles to the direction of heat flow, dT = Temperature difference on the two faces of the body, dx = Thickness of the body, through which the heat flows, taken along the direction of heat flow, and k = Thermal conductivity of the body) A. (Please refer www.indiabix.com) Answer: Option A 15. The heat transfer by conduction through a thick sphere is same as through a thick cylinder. B. False Answer: Option B 16. In aqua-ammonia and Lithium-bromide water absorption refrigeration systems, the refrigerants are respectively D. ammonia and water Answer: Option D 17. As relative humidity decreases, the dew point temperature will be __________ wet bulb temperature. B. lower than Answer: Option B 18. The process of heat transfer from a hot body to a cold body, in a straight line, without affecting the intervening medium , is called radiation. A. True Answer: Option A 19. Reynolds number (RN) is given by (where h = Film coefficient, l = Linear dimension, V = Velocity of fluid, k = Thermal conductivity, t = Temperature, ρ = Density of fluid, cp = Specific heat at constant pressure, and μ = Coefficient of absolute viscosity) C. (Please refer www.indiabix.com) Answer: Option C 20. The optimum effective temperature for human comfort is B. lower in winter than in summer Answer: Option B

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Heat Transfer Refrigeration And Air Conditioning 21. The wet bulb temperature lines, on the psychrometric chart, are curved lines. B. False Answer: Option B 22. The sensible heat factor during cooling and dehumidification process is given by (where h1 = Enthalpy of air entering the cooling coil, h2 = Enthalpy of air leaving the cooling coil, and hA = Enthalpy of air at the end of dehumidification process) A. (Please refer www.indiabix.com) Answer: Option A 23. Thermal diffusivity is a B. physical property of a substance Answer: Option B 24. The condition of refrigerant after leaving the compressor and before entering the condenser is superheated vapour. A. Yes Answer: Option A 25. The total radiation from a black body per second per unit area is __________ fourth power of the absolute temperature. Th is statement is known as Stefan-Boltzmann law. B. directly proportional to Answer: Option B 26. Which of the following represents a heat pump? B. (Please refer www.indiabix.com) Answer: Option B 27. In a psychrometric process, the sensible heat added is 30 kJ/s and the latent heat added is 20 kJ/s. The sensible heat factor for the process will be B. 0.6 Answer: Option B 28. The amount of radiation mainly depends upon the A. nature of the body B. temperature of the body C. type of surface of the body D. all of these Answer: Option D 29. For ammonia refrigerating systems, the tubes of a shell and tube condenser are made of C. steel Answer: Option C 30. The highest thermal diffusivity is of B. lead Answer: Option B 31. While designing the refrigeration system of an aircraft, the prime consideration is that the D. mass of the refrigeration equipment is low Answer: Option D 32. The heat transfer takes place according to C. Second law of thermodynamics Answer: Option C 33. An electrolux refrigerator is called a __________ absorption system. C. three fluids Answer: Option C 34. The heat transfer by radiation __________ a medium. B. does not require Answer: Option B 35. Thermal conductivity of water __________ with rise in temperature. D. may increase or decrease depending upon temperature Answer: Option D 36. During adiabatic saturation process on unsaturated air __________ remains constant. D. wet bulb temperature Answer: Option D 37. The thickness of thermal and hydrodynamic boundary layer is equal if Prandtl number is A. equal to one Answer: Option A 38. A perfect black body is one which B. absorbs heat radiations of all wave lengths falling on it Answer: Option B 39. Degree of saturation or percentage humidity is C. the ratio of the actual mass of water vapour in a unit mass of dry air to the mass of water vapour in the same mass of dry air when it is saturated at the same temperature and pressure. Answer: Option C 40. The coefficient of performance of Heat Pump is always __________ one. C. greater than Answer: Option C 41. During a refrigeration cycle, heat is rejected by the refrigerant in a B. condenser Answer: Option B

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Heat Transfer Refrigeration And Air Conditioning 42. A refrigeration system A. removes heat from a low temperature body and delivers it to a high temperature body Answer: Option A 43. The subcooling in a refrigeration cycle B. increases C.O.P. Answer: Option B 44. Nusselt number (NN) is given by A. (Please refer www.indiabix.com) Answer: Option A 45. During sensible cooling of air __________ decreases. C. dry bulb temperature Answer: Option C 46. The critical radius is the insulation radius at which the resistance to heat flow is B. minimum Answer: Option B 47. In case of solids, the heat transfer takes place according to radiation. B. Incorrect Answer: Option B 48. A water cooled condenser operates at a __________ condensing temperature than an air-cooled condenser. B. lower Answer: Option B 49. The relative humidity decreases as air gets wet. A. True Answer: Option A 50. The temperature of ammonia after compression in a vapour compression system is C. 70 to 110° C Answer: Option C

SECTION-02 1. The centrifugal compressors are generally used for refrigerants that require D. large displacements and low condensing pressures Answer: Option D 2. The water, alcohol and ammonia have same refrigerating effect at different altitudes. B. No Answer: Option B 3. The automobile radiator is a heat exchanger of C. cross flow type Answer: Option C 4. In mechanical refrigeration system, the refrigerant occurs as liquid between condenser and expansion valve. A. True Answer: Option A 5. A heat pump working on a reversed Carnot cycle has a C.O.P. of 5. It works as a refrigerator taking 1 kW of work input. The refrigerating effect will be D. 4 kW Answer: Option D 6. The curved lines on a psychrometric chart indicates D. relative humidity Answer: Option D 7. During humidification process, __________ increases. B. relative humidity Answer: Option B 8. A pressure gauge on the discharge side of a refrigerant compressor reads too high. The reasons will be A. lack of cooling water B. water temperature being high C. dirty condenser surface D. all of these Answer: Option D 9. The counter-current flow heat exchanger can transfer __________ heat than parallel flow heat exchanger. B. more Answer: Option B 10. The freon group of refrigerants are A. halo-carbon refrigerants Answer: Option A 11. For evaporators and condensers, for the given conditions, the logarithmic mean temperature difference (tm) for parallel flow is __________ that for counter flow. A. equal to Answer: Option A 12. A vapour absorption refrigerator uses __________ as a refrigerant. D. aqua-ammonia Answer: Option D 13. Thermal conductivity of air increases with rise in temperature. A. Correct Answer: Option A

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Heat Transfer Refrigeration And Air Conditioning 14. The material of pipe lines for a system using ammonia as a refrigerant should be copper. B. No Answer: Option B 15. The wave length corresponding to the maximum energy is inversely proportional to the absolute temperature. This statement is called Planck's law. B. No Answer: Option B 16. Which of the following refrigerant has the highest freezing point. B. Carbon dioxide Answer: Option B 17. Air conditioning means A. cooling B. heating C. dehumidifying D. all of these Answer: Option D 18. The emissivity for a black body is D. 1 (Please refer www.indiabix.com) Answer: Option D 19. Which of the following would lead to a reduction in thermal resistance? A. In conduction, reduction in the thickness of the material and an increase in thermal conductivity. B. In convection, stirring of the fluid and cleaning the heating surface. C. In radiation, increasing the temperature and reducing the emissivity. D. all of the above Answer: Option D 20. The ratio of the thickness of thermal boundary layer to the thickness of hydrodynamic boundary layer is equal to (Prandtl number)n, where n is equal to A. -1/3 (Please refer www.indiabix.com) Answer: Option A 21. Free convection flow depends on A. density B. coefficient of viscosity C. gravitational force D. all of these Answer: Option D 22. The critical pressure of a liquid is the pressure A. above which a liquid will remain a liquid Answer: Option A 23. Conduction is a process of heat transfer A. from one particle of the body to another without the actual motion of the particles Answer: Option A 24. Thermal diffusivity of a substance is A. directly proportional to the thermal conductivity B. inversely proportional to density of substance C. inversely proportional to specific heat D. all of the above Answer: Option D 25. The sensible heat factor during the heating and humidification process is given by (where h1 = Enthalpy of air entering t he heating coil, h2 = Enthalpy of air leaving the heating coil, and hA = Enthalpy of air at the end of humidification process). D. (Please refer www.indiabix.com) Answer: Option D 26. Fouling factor is used A. in heat exchanger design as a safety factor Answer: Option A 27. The natural convection air cooled condensers are used in A. domestic refrigerators Answer: Option A 28. The process, generally used in winter air-conditioning to warm and humidity the air, is called C. heating and humidification Answer: Option C 29. At 100% relative humidity, wet bulb temperature, dry bulb temperature, dew point temperature and saturation temperature are equal. A. Correct Answer: Option A 30. Bell-Coleman cycle is a C. reversed Joule cycle Answer: Option C 31. Sulphur dioxide is extremely toxic and non-flammable. A. True Answer: Option A 32. The transfer of heat from one body to another takes place only when there is a temperature difference between the bodies. A. Yes Answer: Option A

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Heat Transfer Refrigeration And Air Conditioning 33. A heat exchanger with heat transfer surface area A and overall heat transfer coefficient U handles two fluids of heat capacities Cmax and Cmin. The number of transfer units (NTU) used in the analysis of heat exchanger is specified as D. (Please refer www.indiabix.com) Answer: Option D 34. Thermal diffusivity of a substance is given by (where h = Thermal diffusivity, ρ = Density of substance, S = Specific heat, and k = Thermal conducti vity) A. (Please refer www.indiabix.com) Answer: Option A 35. Which of the following statement is correct for ammonia as a refrigerant? A. It is toxic to mucous membranes. B. it requires large displacement per TR compared to fluoro carbons. C. It reacts with copper and its alloys. D. all of these Answer: Option D 36. The wet bulb temperature at 100% relative humidity is __________ dew point temperature. A. same as Answer: Option A 37. The use of heat exchangers is made in A. radiators in automobile B. condensers and boilers in steam plants C. condensers and evaporators in refrigeration and air conditioning units D. all of the above Answer: Option D 38. In a heat exchanger with one fluid evaporating or condensing, the surface area required is least in A. parallel flow B. counter flow C. cross flow D. all of these Answer: Option D 39. Which of the following statement is correct? B. At thermal equilibrium, the emissivity and absorptivity are same. Answer: Option B 40. The horizontal and uniformly spaced lines on a psychrometric chart indicates relative humidity. B. Incorrect Answer: Option B 41. The sensible heat gain is due to the __________ difference between the fresh air and the air in space. A. temperature Answer: Option A 42. During cooling and dehumidification, dry bulb temperature C. decreases Answer: Option C 43. The coefficient of performance of electrolux refrigerator is the ratio of B. heat absorbed by the evaporator to the heat supplied by the gas burner Answer: Option B 44. The sulphur sticks, in case of leakage of ammonia refrigerant, gives white smoke. A. True Answer: Option A 45. During gas charging in an ammonia vapour compression system, the connection is made at the compressor outlet. A. Agree Answer: Option A 46. The conditioned air supplied to the room must have the capacity to take up C. both room sensible heat and latent heat loads Answer: Option C 47. The process of removing moisture from the air, without change in its dry bulb temperature, is called dehumidification. A. Correct Answer: Option A 48. The specific humidity during dehumidification process C. decreases Answer: Option C 49. Which of the following refrigerant has the lowest freezing point? C. R-22 (Please refer www.indiabix.com) Answer: Option C 50. For a white body, absorptivity (α ) = 0, reflectivity (ρ) = 1 and transmittivity (τ) = 0. A. Correct Answer: Option A

SECTION-03 1. Which of the following refrigerant has the maximum ozone depletion potential in the stratophere? D. Flourine Answer: Option D

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Heat Transfer Refrigeration And Air Conditioning 2. Which of the following statement is correct? A. The constant enthalpy lines are also constant wet bulb temperature lines. B. The wet bulb and dry bulb temperature are equal at saturation condition. C. The wet bulb temperature is a measure of enthalpy of moist air. D. all of the above Answer: Option D 3. According to Stefan's law, the total radiation from a black body per second per unit area is directly proportional to the fourth power of the absolute temperature. A. Correct Answer: Option A 4. In electrolux refrigerator C. ammonia evaporates in hydrogen Answer: Option C 5. Two long parallel surfaces each of emissivity 0.7 are maintained at different temperatures and accordingly have radiation heat exchange between them. It is desired to reduce 75% of the radiant heat transfer by inserting thin parallel shields of emissivity 1 on both sides. The n umber of shields should be C. three Answer: Option C 6. A boot-strap air cooling system has B. two heat exchangers Answer: Option B 7. The boiling point of __________ is -10.5°C. C. sulphur dioxide Answer: Option C 8. One tonne of refrigeration (1TR) means that the heat removing capacity is B. 210 kJ/min Answer: Option B 9. The operating pressure for refrigerating units using R-12 as a refrigerant is B. 8 bar Answer: Option B 10. The specific humidity during heating and humidification process. B. increases Answer: Option B 11. The superheated vapour region, in a pressure enthalpy chart, is represented by the space C. between the saturated liquid line and saturated vapour line Answer: Option C 12. The minimum temperature to which water can be cooled in a cooling tower is B. wet bulb temperature of air Answer: Option B 13. The index which corelates the combined effects of air temperature, relative humidity and air velocity on the human body, is known as B. effective temperature Answer: Option B 14. The ratio of Nusselt number and the product of Reynold's number and Prandtl number is equal to A. Stanton number Answer: Option A 15. The alignment circle is marked on the psychrometric chart at B. 26°C DBT and 50% RH Answer: Option B 16. The C.O.P. of a Carnot refrigerator in winter will be __________ as compared to C.O.P. in summer. C. higher Answer: Option C 17. Which of the following statement is correct? A. The human body can lose heat even if its temperature is less than the atmospheric temperature. B. The increase in air movement increases the evaporation from the human body. C. The warm air increases the rate of radiation of heat from the human body. D. both (a) and (b) Answer: Option D 18. When the temperature of the surrounding is higher than the temperature of the body, then the heat loss by convection from the body to the surrounding will be B. negative Answer: Option B 19. If a gas is to be liquified, its temperature must be C. equal to critical temperature Answer: Option C 20. The thermostatic expansion valve is used in __________ type of evaporators. C. dry Answer: Option C 21. According to Prevost's theory of exchanges, every body irrespective of its temperature continuously emit heat radiations to the surrounding bodies and at the same time receives heat radiations from the surrounding bodies. A. True Answer: Option A

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Heat Transfer Refrigeration And Air Conditioning 22. In a boot-strap air evaporative cooling system, the evaporator is provided D. between the second heat exchanger and the cooling turbine Answer: Option D 23. According to Stefan-Boltzmann law, the total radiation from a black body per second per unit area is directly proportional to the D. fourth power of the absolute temperature Answer: Option D 24. A good refrigerant should have A. high latent heat of vaporisation and low freezing point Answer: Option A 25. The thermal diffusivity for gases is generally __________ those for liquids. C. greater than Answer: Option C 26. The condition of refrigerant after passing through the expansion or throttle valve, in a vapour compression system is C. very wet vapour Answer: Option C 27. The process of adding moisture to the air, without change in its dry bulb temperature, is known as humidification. A. Agree Answer: Option A 28. In case of liquids and gases, the heat transfer takes place according to B. convection Answer: Option B 29. The logarithmic mean temperature difference (tm) is given by (where Δt1 and Δt2 are temperature differences between the h ot and cold fluids at entrance and exit) A. ( Please refer www.indiabix.com) Answer: Option A 30. The radiation emitted by a black body is known as A. black radiation B. full radiation C. total radiation D. all of these Answer: Option D 31. The sensible heat during humidification process decreases. B. False Answer: Option B 32. According to Newton's law of cooling, the heat transfer from a hot body to a cold body is A. directly proportional to the surface area B. directly proportional to the difference of temperatures between the two bodies C. either (a) or (b) D. both (a) and (b) Answer: Option D 33. The freezing point of carbon dioxide is equal to boiling point of R-12. B. Incorrect Answer: Option B 34. The condition of refrigerant as it leaves the compressor in a vapour compression system is D. superheated vapour Answer: Option D 35. The super-heating in a refrigeration cycle C. decreases C.O.P. Answer: Option C 36. Thermal conductivity of a material may be defined as the A. quantity of heat flowing in one second through a slab of the material of area 1 cm2 and thickness 1 cm when its faces differ in temperature by 1° C B. quantity of heat flowing in one second through one cm of material when opposite faces are maintained at a temperature difference of 1° C C. heat conducted in unit time across unit area through unit thickness when a temperature difference of unity is maint ained between opposite faces D. all of the above Answer: Option D 37. During sensible heating of air, specific humidity remains constant. A. Agree Answer: Option A 38. Air refrigeration cycle is used in D. gas liquefaction Answer: Option D 39. Reynolds number is the ratio of C. inertia force to viscous force Answer: Option C 40. The wet bulb depression is zero when relative humidity is D. 1.0 ( Please refer www.indiabix.com) Answer: Option D 41. In a shell and coil condenser, water flows in the shell and the refrigerant in the coil. B. False Answer: Option B

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Heat Transfer Refrigeration And Air Conditioning 42. In a saturated air-water vapour mixture, the C. dry bulb, wet bulb and dew point temperature are same Answer: Option C 43. Dew point temperature corresponds to the saturation temperature of vapour at its partial pressure. A. True Answer: Option A 44. The capillary tube is not used in large capacity refrigeration systems because B. capacity control is not possible Answer: Option B 45. The ratio of emissive power of a body to the emissive power of a perfectly black body is called emissivity. A. Agree Answer: Option A 46. The thermostatic expansion valve operates on the changes in the A. degree of superheat at exit from the evaporator Answer: Option A 47. In a vapour compression system, the condition of refrigerant before entering the expansion or throttle valve is A. high pressure saturated liquid Answer: Option A 48. The freezing point of R-12 is D. -135.8°C ( Please refer www.indiabix.com) Answer: Option D 49. The refrigerant supplied to a compressor must be A. superheated vapour refrigerant Answer: Option A 50. The unit of thermal diffusivity is C. m2/h ( Please refer www.indiabix.com) Answer: Option C

SECTION-04 1. The comfort conditions in air conditioning are at (where DBT = Dry bulb temperature, and RH = Relative humidity) C. 22°C DBT and 60% RH Answer: Option C 2. The dry bulb temperature lines, on the psychrometric chart are A. vertical and uniformly spaced Answer: Option A 3. The pressure at the outlet of a refrigerant compressor is called B. discharge pressure Answer: Option B 4. A simple air cooling system is good for __________ flight speeds. A. low Answer: Option A 5. The highest temperature during the cycle in a vapour compression system occurs after evaporation. B. False Answer: Option B 6. In a psychrometric chart, dew point temperature lines are horizontal and non-uniformly spaced. A. Correct Answer: Option A 7. If the evaporator temperature is kept constant, the coefficient of performance of a refrigeration cycle __________ with the increase in condenser temperature. B. decreases Answer: Option B 8. The by-pass factor, in case of sensible cooling of air, is given by (where td1 = Dry bulb temperature of air entering the cooling coil, td2 = Dry bulb temperature of air leaving the cooling coil, and td3 = Dry bulb temperature of the cooling coil) B. (Please refer www.indiabix.com) Answer: Option B 9. The evaporator used in house-hold refrigerators is A. frosting evaporator Answer: Option A 10. The drier in a refrigeration system removes moisture in the system. A. Correct Answer: Option A 11. The __________ point of ammonia is -77.7°C. A. freezing Answer: Option A 12. Sulphur dioxide has the lowest boiling point. B. No Answer: Option B 13. For a given dry bulb temperature, as the relative humidity __________ the wet bulb temperature will increase. B. decreases Answer: Option B

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Heat Transfer Refrigeration And Air Conditioning 14. The lowest thermal diffusivity is of D. rubber Answer: Option D 15. A low wet bulb temperature indicates very __________ humidity. A. low Answer: Option A 16. The operating temperature of a cold storage is - 2° C. The heat leakage from the surrounding is 30 kW for the ambient temperature of 40° C. The actual C.O.P. of refrigeration plant used is one fourth that of ideal plant working between the same temperatures. The power required to drive the plant is D. 18.6 kW (Please refer www.indiabix.com) Answer: Option D 17. In chemical dehumidification process, A. dew point temperature decreases B. wet bulb temperature decreases C. dry bulb temperature increases D. all of these Answer: Option D 18. A one tonne refrigerating machine means that D. one tonne of ice when melts from and at 0° C in 24 hours, the refrigeration effect is equivalent to 210 kJ/min Answer: Option D 19. The air cooling system mostly used in transport type aircrafts is C. boot-strap air cooling system Answer: Option C 20. The critical thickness of insulation is the ratio of thermal conductivity of the insulating material (k) to the heat transfer coefficient at the outer surface of the insulation (h0). A. True Answer: Option A 21. In counter-current flow heat exchanger, the logarithmic temperature difference between the fluids is __________ as compared to parallel flow heat exchanger. C. greater Answer: Option C 22. Environmental protection agencies advice against the use of chloro-fluoro-carbon refrigerants since D. these react with ozone layer Answer: Option D 23. When the lower temperature of a refrigerating machine is fixed, then the coefficient of performance can be improved by D. lowering the higher temperature Answer: Option D 24. The refrigerant carbon dioxide is not widely used because of its __________ power require ments per tonne of refrigeration and high operating pressures. B. high Answer: Option B 25. The by-pass factor of a cooling coil decreases with A. decrease in fin spacing and increase in number of rows Answer: Option A 26. Dehydration is the process of removing water vapour from the surrounding air. A. True Answer: Option A 27. The cooling of air, without any change in its specific humidity, is known as sensible cooling. A. Correct Answer: Option A 28. The capacity of the cooling tower and spray ponds __________ as the wet bulb temperature of air decreases. A. increases Answer: Option A 29. A mixture of dry air and water vapour, when the air has diffused the maximum amount of water vapour into it, is called C. saturated air Answer: Option C 30. The total pressure exerted by the mixture of air and water vapour is equal to the sum of pressures which each constituent would exert, if it occupied the same space by itself. This statement is called C. Dalton's law of partial pressures Answer: Option C 31. The expansion valve in a refrigerator controls the flow of refrigerant. A. Correct Answer: Option A 32. Upto the critical radius of insulation, A. added insulation will increase heat loss Answer: Option A 33. The relative humidity lines on a psychrometric chart are D. curved lines Answer: Option D 34. The C.O.P. of a heat pump working on a reversed Carnot cycle is D. (Please refer www.indiabix.com) Answer: Option D

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Heat Transfer Refrigeration And Air Conditioning 35. A vapour absorption refrigeration system B. gives quiet operation Answer: Option B 36. The rato of energy transferred by convection to that by conduction is called B. Nusselt number Answer: Option B 37. A refrigerating system operating on reversed Brayton refrigeration cycle is used for maintaining 250 K. If the temperature at the end of constant pressure cooling is 300 K and rise in the temperature of air in the refrigerator is 50 K, then the net work of compression will be (assume air as working substance with cp = 1 kJ/kg) B. 50 kJ/kg (Please refer www.indiabix.com) Answer: Option B 38. Wet bulb temperature indicates the moisture content in air. A. Agree Answer: Option A 39. A designer chooses the values of fluid flow rates and specific heats in such a manner that the heat capacities of the two fluids are equal. A hot fluid enters the counter flow heat exchanger at 100° C and leaves at 60° C. A cold fluid enters the heat exchanger at 40° C. The mean temperature difference between the two fluids is A. 20°C (Please refer www.indiabix.com) Answer: Option A 40. The inclined and non-uniformly spaced straight lines on a psychrometric chart indicates wet bulb temperature. A. Agree Answer: Option A 41. The heat transfer by conduction through a thick cylinder(Q) is given by (where T1 = Higher temperature, T2 = Lower temperature, r1 = Inside radius, r2 = Outside radius, l = Length of cylinder, and k = Thermal conductivity) A. (Please refer www.indiabix.com) Answer: Option A 42. The heat is transferred by conduction, convection and radiation in B. boiler furnaces Answer: Option B 43. A thermostatic expansion valve in a refrigeration system A ensures the evaporator completely filled with refrigerant of the load Answer: Option A 44. The temperature rise, between the condenser outlet and expansion valve in ammonia vapour compression system, should be as low as possible. A. Yes Answer: Option A 45. The ratio of the actual mass of water vapour in a unit mass of dry air to the mass of water vapour in the same mass of dry air when it is saturated at the same temperature and pressure, is called D. degree of saturation Answer: Option D 46. For unsaturated air, the dew point temperature is __________ wet bulb temperature. B. less than Answer: Option B 47. During dehumidification process, __________ remains constant. C. dry bulb temperature Answer: Option C 48. Pressure of water vapour is given by A. (Please refer www.indiabix.com) B. (Please refer www.indiabix.com) C. (Please refer www.indiabix.com) D. none of these Answer: Option D 49. The value of the wave length for maximum emissive power is given by C. Wein's law Answer: Option C 50. Emissivity of a body will be equal to its absorptivity at all temperatures. B. No Answer: Option B

SECTION-05 1. R-12 is generally preferred over R-22 in deep freezers since C. it is miscible with oil over large range of temperatures Answer: Option C 2. The temperature of air recorded by a thermometer, when its bulb is surrounded by a wet cloth exposed to the air, is called A. wet bulb temperature Answer: Option A 3. During sub-cooling, sensible heat from a liquid refrigerant is removed. A. Yes Answer: Option A 4. The expression is used for calculating relative humidity. (Please refer www.indiabix.com) B. No Answer: Option B (Please refer www.indiabix.com)

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Heat Transfer Refrigeration And Air Conditioning 5. If the energy radiated per second per sq. cm. of the surface for wave lengths lying between λ, and λ + dλ is represented b y (eλ.dλ), then eλ is called B. emissive power (Please refer www.indiabix.com) Answer: Option B 6. Dry bulb temperature is the temperature of air recorded by a thermometer, when A. it is not affected by the moisture present in the air Answer: Option A 7. In a spray washing system, if the temperature of water is higher than the dry bulb temperature of entering air, then the air is B. heated and humidified Answer: Option B 8. A valve which maintains a constant degree of superheat at the end of the evaporator coil, is called D. low side float valve Answer: Option D 9. The atmospheric air at dry bulb temperature of 15°C enters a heating coil maintained at 40°C. The air leaves the heating c oil at 25°C. The by-pass factor of the heating coil is C. 0.6 (Please refer www.indiabix.com) Answer: Option C 10. An infinite parallel planes with emissivities e1 and e2, the interchange factor for radiation from surface 1 to surface 2 is given by A. (Please refer www.indiabix.com) Answer: Option A 11. The final relative humidity of the air during cooling and dehumidification is generally __________ than that of entering air. B. higher Answer: Option B 12. The emissivity of a polished silver body is __________ as compared to black body. C. very low Answer: Option C 13. In a pressure enthalpy chart, the space between the saturated liquid line and saturated vapour line, represents sub-cooled liquid region. B. False Answer: Option B 14. R-11 has the highest critical point temperature. A. Correct Answer: Option A 15. The ratio of heat extracted in the refrigerator to the workdone on the refrigerant is called A. coefficient of performance of refrigeration Answer: Option A 16. Air refrigerator works on A. reversed Carnot cycle B. Bell Coleman cycle C. both (a) and ib) Answer: Option C 17. The reciprocating refrigerant compressors are very suitable for C. small displacements and high condensing pressures Answer: Option C 18. The boiling point of carbon dioxide is D. -78.3°C (Please refer www.indiabix.com) Answer: Option D 19. The mass of water vapour present in __________ is called absolute humidity. B. 1 m3 of dry air Answer: Option B 20. The relative coefficient of performance is equal to B. (Please refer www.indiabix.com) Answer: Option B 21. The cooling system used for supersonic aircrafts and rockets is D. regenerative air cooling system Answer: Option D 22. Which of the following statement is correct? A. In vapour absorption refrigerator, the compression of refrigerent is avoided. B. Sub-cooling can be achieved by circulating more quantity of cooling water through the condenser. C. In vapour compression refrigeration, the vapour is drawn in the compressor cylinder during its suction stroke and is compress ed adiabatically during the compression stroke. D. all of the above Answer: Option D 23. The desirable property of a refrigerant is A. low boiling point B. high critical temperature C. high latent heat of vaporisation D. all of these Answer: Option D 24. The humidification process, on the psychrometric chart is shown by B. vertical line Answer: Option B

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Heat Transfer Refrigeration And Air Conditioning 25. The colour of the flame of halide torch, in case of leakage of freon refrigerant, will change to A. bright green Answer: Option A 26. The wet bulb depression indicates __________ humidity of the air. B. relative Answer: Option B 27. The refrigerant widely used in domestic refrigerators is D. R-12 Answer: Option D 28. When absorptivity (α) = 1, reflectivity (ρ) = 0 and transmittivity (τ) = 0, then the body is said to be a A. black body Answer: Option A 29. Prandtl number (PN) is given by PN = μ.cp/k. A. Yes Answer: Option A 30. In a vapour compression system, the condition of refrigerant before passing through the condenser is D. superheated vapour Answer: Option D 31. A composite slab has two layers of different materials with thermal conductivities k1 and k2. If each layer has the same thickness, then the equivalent thermal conductivity of the slab will be D. (Please refer www.indiabix.com) Answer: Option D 32. The critical temperature is the temperature D. above which a gas will never liquified Answer: Option D 33. The evaporator changes the low pressure liquid refrigerant from the expansion valve into C. low pressure vapour refrigerant Answer: Option C 34. For air conditioning the operation theatre in a hospital, the percentage of outside air in the air supplied is D. 100 Answer: Option D 35. In case ofsensible cooling of air, the coil efficiency is given by B. 1 - B.P.F. (Please refer www.indiabix.com) Answer: Option B 36. The mass of water vapour present in 1 kg of dry air, is called humidity ratio. A. True Answer: Option A 37. In a vapour compression refrigeration system, a throttle valve is used in place of an expander because C. the positive work in isentropic expansion of liquid is very small Answer: Option C 38. The unit of overall coefficient of heat transfer is A. W/m2K Answer: Option A 39. Most thermostatic expansion valves are set for a superheat of A. 5°C (Please refer www.indiabix.com) Answer: Option A 40. For large tonnage (more than 200 TR) air-conditioning applications, the compressor recommended is C. centrifugal Answer: Option C 41. The ratio of actual mass of water vapour in a given volume of moist air to the mass of water vapour in the same volume of sat urated air at the same temperature and pressure, is called B. relative humidity Answer: Option B 42. The transfer of heat by molecular collision is smallest in C. gases Answer: Option C 43. During dehumidification process, the relative humidity C. decreases Answer: Option C 44. The space between the two walls of a thermos flask is evacuated because vacuum is a __________ conductor of heat. B. bad Answer: Option B 45. The ratio of actual heat transfer to the maximum possible heat transfer is known as heat exchanger effectiveness. A. Agree Answer: Option A 46. When the discharge pressure is too high in a refrigeration system, high pressure control is installed to stop the compres sor. A. Correct Answer: Option A 47. A grey body is one whose absorptivity does not vary with temperature and wave length of the incident ray. A. True Answer: Option A

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Heat Transfer Refrigeration And Air Conditioning 48. The wet bulb temperature during sensible cooling of air C. decreases Answer: Option C 49. In absorption vapour systems, the refrigerant widely used is R-12. B. Incorrect Answer: Option B 50. Hydrogen is used in electrolux refrigeration system so as to __________ the rate of evaporation of the liquid ammonia passing through the evaporator. C. increase Answer: Option C

SECTION-06 1. A condenser of refrigeration system rejects heat at the rate of 120 kW, while its compressor consumes a power of 30 kW. The coefficient of performance of the system will be D. 4 (Please refer www.indiabix.com) Answer: Option D 2. A refrigerant with the highest critical pressure is D. Ammonia Answer: Option D 3. In a shell and tube heat exchanger, baffles are provided on the shell side to A. improve heat transfer B. provide support for tubes C. prevent stagnation of shell side fluid D. all of these Answer: Option D 4. The average value of thermal conductivity for water at 20° C saturate is about 0.51. A. True Answer: Option A 5. In aqua-ammonia absorption refrigeration system, incomplete rectification leads to accumulation of water in A. condenser Answer: Option A 6. The boiling point of ammonia is C. -33.3°C Answer: Option C 7. The by-pass factor (B. P. F.) in case of sensible heating of air is (Where td1 = Dry bulb temperature of air entering the heating coil, td2 = Dry bulb temperature of air leaving the heating coil, and td3 = Dry bulb temperature of heating coil) B. (Please refer www.indiabix.com) Answer: Option B 8. The refrigerant used for absorption refrigerators working on heat from solar collectors is a mixture of water and C. lithium bromide Answer: Option C 9. In a black body, all radiations are rejected. B. False Answer: Option B 10. Most air cooled condensers are designed to operate with a temperature difference of C. 14°C Answer: Option C 11. In a reversed Brayton cycle, the heat is absorbed by the air during D. constant pressure expansion process Answer: Option D 12. Wet bulb temperature is the temperature of air recorded by a thermometer, when B. its bulb is surrounded by a wet cloth exposed to the air Answer: Option B 13. A device used for transfering heat from one fluid to another is called heat exchanger. A. True Answer: Option A 14. The coefficient of performance (C.O.P.) of a refrigerator working as a heat pump is given by B. (C.O.P.)P = (C.O.P.)R + 1 (Please refer www.indiabix.com) Answer: Option B 15. The temperature below which a gas is always liquified, is known as critical temperature. B. Incorrect Answer: Option B 16. A Bell Coleman refrigerator working on dense air system as compared to open air system, for the same range of temperature, results in higher coefficient of performance. A. Agree Answer: Option A 17. The ratio of surface convection resistance to the internal conduction resistance is known as B. Biot number Answer: Option B

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Heat Transfer Refrigeration And Air Conditioning 18. Relative humidity is given by (where pv = Partial pressure of water vapour, pb = Barometric pressur e, ps = Pressure of saturated air, pd = Pressure at dry bulb temperature, pw = Saturation pressure corresponding to wet bulb temperature, and μ = Degree of saturation) B. (Please refer www.indiabix.com) Answer: Option B 19. Kirchhoff's law states that C. the ratio of the emissive power and absorptive power of all bodies is the same and is equal to the emissive power of a perfec tly black body Answer: Option C 20. Dew point temperature is the temperature of air recorded by a thermometer, when the moisture present in it begins to condense. A. Correct Answer: Option A 21. The expression is used for calculating B. humidity ratio Answer: Option B 22. The critical thickness of insulation for a sphere is B. 2k/h0 (Please refer www.indiabix.com) Answer: Option B 23. The difference between dry bulb temperature and dew point temperature, is called C. dew point depression Answer: Option C 24. Logarithmic mean temperature difference is the same as the arithmetic mean temperature difference. B. Disagree Answer: Option B 25. Film coefficient is defined as the ratio of A. thermal conductivity to the equivalent thickness of the film of fluid Answer: Option A 26. Planck's law holds good for all coloured bodies. A. True Answer: Option A 27. In mechanical refrigeration system, the refrigerant has the maximum temperature C. between compressor and condenser Answer: Option C 28. The capacity of a domestic refrigerator is in the range of A. 0.1 to 0.3 TR (Please refer www.indiabix.com) Answer: Option A 29. The condition of refrigerant after passing through the condenser in a vapour compression system is A. saturated liquid Answer: Option A 30. The leakage in a refrigeration system using freon is detected by A. halide torch Answer: Option A 31. If the condenser temperature is kept constant, the coefficient of performance of a refrigeration cycle increases with the increase in evaporat or temperature. A. Yes Answer: Option A 32. The process of heat transfer from one particle of the fluid to another by the actual movement of the fluid particles caused by some mechanical means, is known as C. forced convection Answer: Option C 33. When α is absorptivity, ρ is reflectivity and τ is transmittivity, then for a diathermanous body, (Please refer www.indiabix.com) D. α + ρ = 1 and τ = 0 (Please refer www.indiabix.com) Answer: Option D 34. When there is an addition of water vapour to the air of enclosed space, a gain in __________ is said to occur. B. latent heat Answer: Option B 35. The relative humidity __________ as air gets drier. A. increases Answer: Option A 36. The central air conditioning system has __________ overall efficiency as compared to individual systems. C. higher Answer: Option C 37. The ratio of the emissive power and absorptive power of all bodies is the same and is equal to the emissive power of a perfectly black body. This statement is known as C. Kirchhoff's law Answer: Option C 38. An ordinary passenger aircraft requires a cooling system of capacity. C. 8 TR Answer: Option C 39. In air-conditioning of aeroplanes, using air as a refrigerant, the cycle used is C. reversed Brayton cycle Answer: Option C

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Heat Transfer Refrigeration And Air Conditioning 40. The thermal diffusivity for solids is generally less than those for liquids and gases. B. False Answer: Option B 41. Conduction is the process of heat transfer from one particle of the body to another by the actual motion of the heated particles. B. False Answer: Option B 42. Moisture should be removed from refrigerants to avoid A. freezing at the expansion valve B. restriction to refrigerant flow C. corrosion of steel plates D. all of these Answer: Option D 43. Which of the following statement is wrong? A. The value of C.O.P. is always greater than one. B. In a vapour compression system, the condition of refrigerant before entering the compressor is dry saturated vapour. C. The space between the saturated liquid line and saturated vapour line, in a pressure enthalpy chart, is wet vapour region. D. none of the above Answer: Option D 44. During humidification process, dry bulb temperature A. remains constant Answer: Option A 45. Fourier's law of heat conduction gives the heat flow for C. one dimensional cases only Answer: Option C 46. The product of Reynolds number and Prandtl number is known as C. Peclet number Answer: Option C 47. Carbon dioxide is A. colourless B. odourless C. non-flammable D. all of these Answer: Option D 48. The reduced ambient air cooling system has C. two cooling turbines and one heat exchanger Answer: Option C 49. The heat of sun reaches to us according to C. radiation Answer: Option C 50. The specific humidity during humidification process B. increases Answer: Option B

SECTION-07 1. Sensible heat factor is given by (where S.H. = Sensible heat, and L.H. = Latent heat) A. (Please refer www.indiabix.com) Answer: Option A 2. Stefan-Boltzmann law is applicable for heat transfer by convection. B. Disagree Answer: Option B 3.The most commonly used method for the design of duct size is the C. static regain method Answer: Option C 4. In counter-current flow heat exchangers A. both the fluids at inlet are in their hottest state Answer: Option A 5. The rate of heat flow through a body is . The term x/kA is known as B. thermal resistance Answer: Option B 6. In a vapour compression system, the condition of refrigerant is dry saturated vapour A. before entering the compressor Answer: Option A 7. An evaporator is also known as A. freezing coil B. cooling coil C. chilling coil D. all of these Answer: Option D 8. The rate of heat flow through a body is . The term is known as temperature gradient. A. Yes Answer: Option A

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Heat Transfer Refrigeration And Air Conditioning 9. Oil separator in a refrigeration cycle is installed B. between compressor and condenser Answer: Option B 10. In larger industrial and commercial reciprocating compression systems, refrigerent widely used is A. ammonia Answer: Option A 11. During sensible cooling of air, specific humidity A. remains constant Answer: Option A 12. The transfer of heat by molecular collision is known as A. conduction Answer: Option A 13. When tc1 and tc2 are the temperatures of cold fluid at entry and exit respectively and th1 and th2 are the temperatures of hot fluid at entry and exit point, and cold fluid has lower heat capacity rate as compared to hot fluid, then effectiveness of the heat exchanger is given by D. (Please refer www.indiabix.com) Answer: Option D 14. In a psychrometric chart, specific humidity (moisture content) lines are B. horizontal and uniformly spaced Answer: Option B 15. The expression Q = ρ AT4 is called (Please refer www.indiabix.com) B. Stefan-Boltzmann equation (Please refer www.indiabix.com) Answer: Option B 16. Thermal conductivity of solid metals __________ with rise in temperature. B. decreases Answer: Option B 17. The horizontal and non-uniformly spaced lines on a psychrometric chart indicates C. dew point temperature Answer: Option C 18. A reversible engine has ideal thermal efficiency of 30%. When it is used as a refrigerating machine with all other conditions unchanged, the coefficient of performance will be B. 2.33 (Please refer www.indiabix.com) Answer: Option B 19. Which of the following refrigerant is highly toxic and flammable? A. Ammonia Answer: Option A 20. The unit of Stefan-Boltzmann constant is C. Watt/m2K4 (Please refer www.indiabix.com) Answer: Option C 21. The emissive power of a body depends upon its A. temperature B. physical nature C. wave length D. all of these Answer: Option D 22. An electric cable of aluminium conductor (k = 240 W/mK) is to be insulated with rubber (k = 0.15 W/mK). The cable is to be located in air (h = 6 W/m2). The critical thickness of insulation will be A. 25 mm Answer: Option A 23. A cube at high temperature is immersed in a constant temperature bath. It loses heat from its top, bottom and side surfaces with heat transfer coefficients of h1, h2 and h3 respectively. The average heat transfer coefficient for the cube is A. h1 + h2 + h3 (Please refer www.indiabix.com) B. (h1h2h3)1/3 (Please refer www.indiabix.com) C. (Please refer www.indiabix.com) D. none of these (Please refer www.indiabix.com) Answer: Option D 24. The dehumidification process, on the psychrometric chart, is shown by B. vertical line Answer: Option B 25. The vertical and uniformly spaced lines on a psychrometric chart indicates A. dry bulb temperature Answer: Option A 26. In case of sensible heating of air, the coil efficiency is given by (where B.P.F. = By-pass factor) B. 1 - B.P.F. (Please refer www.indiabix.com) Answer: Option B 27. The coefficient of performance (C.O.P.) is the reciprocal of the efficiency of a heat engine. A. True Answer: Option A 28. The wet bulb temperature at 100% relative humidity is __________ dry bulb temperature. A. same as Answer: Option A

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Heat Transfer Refrigeration And Air Conditioning 29. The freezing point of sulphur dioxide is B. -75.2°C Answer: Option B 30. The ratio of the energy absorbed by the body to the total energy falling on it, is called A. absorptive power Answer: Option A 31. The coefficient of performance of a domestic refrigerator is __________ as compared to a domestic air-conditioner. B. less Answer: Option B 32. The process of heat transfer from one particle of the body to another is called conduction, when the particles of the body B. do not move actually Answer: Option B 33. The human body feels comfortable when the heat stored in the body is C. zero Answer: Option C 34. A Bell Coleman refrigerator working on dense air system as compared to open air system, for the same range of temperature, results in __________ power per tonne of refrigeration. B. lower Answer: Option B 35. The amount of heat flow through a body by conduction is A. directly proportional to the surface area of the body B. directly proportional to the temperature difference on the two faces of the body C. inversely proportional to the thickness of the body D. all of the above Answer: Option D 36. A furnace is made of a red brick wall of thickness 0.5 m and conductivity 0.7 W/mK. For the same heat loss and temperature dr op, this can be replaced by a layer of diatomite earth of conductivity 0.14 W/mK and thickness B. 0.1 m (Please refer www.indiabix.com) Answer: Option B 37. In a refrigeration system, the expansion device is connected between the C. receiver and evaporator Answer: Option C 38. The heat rejection factor (HRF) is given by C. (Please refer www.indiabix.com) Answer: Option C 39. Wein's law states that the wave length corresponding to __________ is proportional to the absolute temperature. B. maximum energy Answer: Option B 40. In a domestic vapour compression refrigerator, the refrigerant commonly used is C. R-12 Answer: Option C 41. In order to cool and dehumidify a stream of moist air, it must be passed over the coil at a temperature C. which is lower than the dew point temperature of the incoming stream Answer: Option C 42. The coefficient of performance of vapour compression refrigeration system is quite __________ as compared to air refrigeration system. B. high Answer: Option B 43. In order to collect liquid refrigerant and to prevent it from going to a __________ , a device known as accumulator is used at the suction of compressor. A. compressor Answer: Option A 44. Which of the following refrigerant has the lowest boiling point? B. Carbon dioxide Answer: Option B 45. During sensible cooling of air, the relative humidity increases. A. Yes Answer: Option A 46. In actual air-conditioning applications for R-12 and R-22, and operating at a condenser temperature of 40° C and an evaporator temperature of 5° C, the heat rejection factor is about B. 1.25 (Please refer www.indiabix.com) Answer: Option B 47. The undesireable property of a refrigerant is D. high boiling point Answer: Option D 48. The dry bulb temperature during sensible heating of air B. increases Answer: Option B 49. Radiation is the process of heat transfer in which heat flows from a __________ , in a straight line, without affecting the intervening medium. B. hot body to cold body Answer: Option B

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Heat Transfer Refrigeration And Air Conditioning 50. The heating of air, without any change in its specific humidity, is known as sensible heating. A. True Answer: Option A

SECTION-08 1. The heat transfer from a hot body to a cold body is directly proportional to the surface area and difference of temperatur es between the two bodies. This statement is called B. Newton's law of cooling Answer: Option B 2. The pressure at the inlet of a refrigerant compressor is called A. suction pressure Answer: Option A 3. The process, generally used in summer air conditioning to cool and dehumidify the air, is called D. cooling and dehumidification Answer: Option D 4. The leakage in a refrigeration system using ammonia is detected by B. sulphur sticks Answer: Option B 5. The lowest temperature during the cycle in a vapour compression system occurs after D. evaporation Answer: Option D 6. The temperature of air recorded by a thermometer, when it is not effected by the moisture present in the air, is called B. dry bulb temperature Answer: Option B 7. A human body feels comfortable when the heat produced by the metabolism of human body is equal to the A. heat dissipated to the surroundings B. heat stored in the human body C. sum of (a) and (b) D. difference of (a) and (b) Answer: Option C 8. During sensible cooling, D. partial pressure of vapour remains constant Answer: Option D 9. The wave length of the radiation emitted depends only on the temperature and is independent of the material of the body. A. True Answer: Option A 10. The process of heat transfer from one particle of the body to another by the actual motion of the heated particles, is called B. convection Answer: Option B 11. In a domestic refrigerator, a capillary tube controls the flow of refrigerant from the D. condenser to the evaporator Answer: Option D 12. The absolute humidity is the mass of water vapour present in 1 m3 of dry air. A. Agree Answer: Option A 13. In a vapour absorption refrigeration system, the compressor of the vapour compression system is replaced by D. absorber, generator and liquid pump Answer: Option D 14. The refrigerant used in small-tonnage commercial machines (hermetically sealed units) is C. sulphur dioxide Answer: Option C 15. In a lithium bromide absorption refrigeration system B. water is used as a refrigerant and lithium bromide as an absorbent Answer: Option B 11. In a domestic refrigerator, a capillary tube controls the flow of refrigerant from the D. condenser to the evaporator Answer: Option D 12. The absolute humidity is the mass of water vapour present in 1 m3 of dry air. A. Agree Answer: Option A 13. In a vapour absorption refrigeration system, the compressor of the vapour compression system is replaced by D. absorber, generator and liquid pump Answer: Option D 14. The refrigerant used in small-tonnage commercial machines (hermetically sealed units) is C. sulphur dioxide Answer: Option C 15. In a lithium bromide absorption refrigeration system B. water is used as a refrigerant and lithium bromide as an absorbent Answer: Option B

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Heat Transfer Refrigeration And Air Conditioning 21. It is desired to condition the outside air from 70% relative humidity and 45° C dry bulb temperature to 50% relative humidity and 25° C dry bulb temperature (room condition). The practical arrangement will be C. cooling and dehumidification Answer: Option C 22. During heating and dehumidification process, dry bulb temperature B. increases Answer: Option B 23. The C.O.P. of a refrigerator working on a reversed Carnot cycle is (where T1 = Lowest absolute temperature, and T2 = Highest absolute temperature) A. (Please refer www.indiabix.com) Answer: Option A 24. A refrigerant compressor is used to A. raise the pressure of the refrigerant B. raise the temperature of the refrigerant C. circulate the refrigerant through the refrigerating system D. all of the above Answer: Option D 25. In which of the following refrigeration system, waste heat can be effectively used? B. Vapour absorption cycle Answer: Option B 26. During heating and humidification, the final relative humidity of air C. can be lower or higher than that of the entering air Answer: Option C 27. The fluids used in electrolux refrigerator are C. ammonia, water and hydrogen Answer: Option C 28. The process of undercooling is generally brought about by A. circulating more quantity of cooling water through the condenser B. using water colder than the main circulating water C. employing a heat exchanger D. any one of the above Answer: Option D 29. The refrigerant after condensation process is cooled below the saturation temperature before throttling. Such a process is called A. sub-cooling or under-cooling Answer: Option A 30. R-12 has the __________ freezing point. A. lowest Answer: Option A 31. The power per tonne of refrigeration is A. 3.5/C.O.P. ( Please refer www.indiabix.com) Answer: Option A 32. The process of heat transfer from one particle of the fluid to another by the actual movement of the fluid particles due to difference of density caused by temperature of the particle is known as B. free convection Answer: Option B 33. The thermostatic expansion valve is also called C. constant superheat valve Answer: Option C 34. In figure shown, E is a heat engine with efficiency of 0.4 and R is a refrigerator. It is given that Q2 + Q4 = 3Q1. The C.O.P. of the refrigerator is D. 5.0 ( Please refer www.indiabix.com) Answer: Option D 35. The specific humidity during cooling and dehumidification C. decreases Answer: Option C 36. The capillary tube, as an expansion device, is used in A. domestic refrigerators B. water coolers C. room air conditioners D. all of these Answer: Option D 37. In aircraft, air refrigeration Cycle is used because of A. low weight per tonne of refrigeration Answer: Option A 38. The material of pipe lines for a system using freon as a refrigerant should be B. copper Answer: Option B 39. The temperature of air recorded by a thermometer, when the moisture present in it begins to condense, is called wet bulb temp erature. B. No Answer: Option B

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Heat Transfer Refrigeration And Air Conditioning 40. In a pressure enthalpy chart, the space to the left of the saturated liquid line represents C. sub-cooled liquid region Answer: Option C 41. During sensible heating of air __________ decreases. B. relative humidity Answer: Option B 42. The overall coefficient of heat transfer is used in problems of D. conduction and convection Answer: Option D 43. The boiling point of R-12 is about - 30°C. A. True Answer: Option A