Heat Transfer Elements PDF

Heat Transfer Elements Prepared By: Engr. Mark Niño B. Javier, ME,MSEE 1. One of the reasons for insulating the pipes is: A. They may not break under pressure B. There is maximum corrosion C. Capacity to withstand pressure is increased D. Heat loss from the surface is minimized 2...

Heat Transfer Elements Prepared By: Engr. Mark Niño B. Javier, ME,MSEE 1. One of the reasons for insulating the pipes is: A. They may not break under pressure B. There is maximum corrosion C. Capacity to withstand pressure is increased D. Heat loss from the surface is minimized 2. The rate of radiant energy, that is emitted by a surface at any temperature and in small wavelengths is found from the known rate of energy, that under the same conditions will be emmitted from a black surface, by multiplying with the absorptivity. The above enunciation is called; A. Lambert’s law B. Kirchhoff’s law C. Planck’s law D. Stefan Boltzmann’s law 3. Which of the following is generally used to measure that temperature inside the furnace? A. Mercury thermometer B. alcohol thermometer C. ash thermometer D. optical pyrometer 4. All heat transfer processes: A. involve transfer of energy B. involve temperature difference between the bodies C. obey first law of thermodynamics D. obey second law of thermodynamics 5. What is thermal diffusivity? A. a mathematical formula B. a physical property of the material C. a configuration for heat conduction D. a dimensionless parameter 6. which of the following is a unit of thermal diffusivity? A. m/hr B. kcal/m hr C. kcal/m hr ˚C D. m/ hr ˚C 7. Non- isotropic condutivity is shown by which of the following? A. brass B. copper C. wood D. steel 8. for glass wool thermal conductivity changes from sample due changes in; A. structure B. density C. composition D. all of the above 9. which of the following is the S.I unit of thermal conductivity? A. W/m-hr-˚K B. W/m ˚K C. KJ/m-hr-˚C D. M/m-hr-˚C 10. What is the value of the Prandt’l number for air? A. 10 B. 6.7 C. 67 D. 0.7 11. According to prevost theory of heat exchange? A. it is impossible to transfer heat from low temperature source to high temperature source B. heat transfer by radiation needs no medium C. all bodies above absolute zero emit radiation D. heat transfer in most of the cases occurs by combination of conduction, convection and radiation 12. Thermal conductivity of wood depends on which of the following A. moisture B. temperature C. density D. all of the above 13. A fur coat on an animal will help the animal to remain; A. warm in winter B. cool in winter C. warm in summer D. warm in summer 14. The nature of flow of a fluid inside a tube, whether it is turbulent or laminar, can be ascertained by; A. Flow of velocity B. flow of current C. flow of density D. flow of water 18. The statement that the emissivity and absorptivity of a surface is surrounded by its own temperature are the same for both monochromatic and total radiation is called: A. lambert’s law B. kirchhoff’s law C. D’ Alambart’s D. law of emissivity 19. A reservoir that supplies energy in the form of heat is called: A. source B. sink C. cold reservoir D. heat reservoir 20. in regenerator type heat exchanger, heat transfer occurs by: A. direct mixing of hot and cold fluids B. a complete separation between hot and cold fluids C. flow of hot and cold fluid alternately over a surface D. generation of heat again and again 21. least value of Prandt’l number can be expected in case of A. liquid metals B. sugar solution C. salt solution D. water 22. “The boiling point of a solution is a linear function of water at the same pressure” The above statement is called A. Dubring’s rule B. Petit and Dulong’s law C. Fick’s rule D. Reynolds law 23. Floating heads are provided in heat exchangers to A. increase pressure drop B. decrease the pressure drop C. facilitate maintenance D. avoid deformation of tubes because of thermal expansion 24. What do you call the first stage of crystal formation? A. nucleation B. foaming C. separation D. vortexing 25. in heat exchanger design, one transfer unit implies: A. one fluid which is exchanging with another fluid of the same chemical composition B. the section of heat exchanger which will cause temperature drop of one degree centigrade C. the section of heat exchanger where heat transfer surface area has been one square meter D. condition when the change in temperature of one steam is numerically equal to the average driving force 26. Dritus Boelter equation can be applied in case of fluid flowing in: A. Transition region B. turbulent region C. laminar region D. any of the above 27. in sugar mills can just is evaporated in: A. zigzag tube evaporators B. long vertical tube evaporators C. short vertical evaporators D. horizontal tube evaporators 28. A 1-2 heat exchanger refers to which of the following? A. single pass on shell side and double pass on tube side B. single pass on tube side and double pass on shell side C. single liquid cools two liquid at different temperature D. two tubes of cold fluid pass though one tube of hot fluid 29. A correction of LMTD is essential in case of: A. parallel flow heat exchanger B. counter current heat exchanger C. cross flow heat exchanger D. none of the above. 30. Which of the following is used as entrainer in acetic acid – water separation? A. methyl alcohol B. phosphorous C. butyl acetate D. hexane 31. A type of radiation consisting of singly charged particles that generate to intermediate distance. A. Nuclear radiation B. Alpha radiation C. Beta radiation D. Gamma radiation 32. an electrically charged atom or radical which carries electricity through an electrolyte is called: A. ion B. isotope C. molecule D. hole 33. The energy of a body that can be transmitted in the form of heat. A. Heat energy B. Thermal energy C. Entropy D. Internal enrgy 34. In an isometric process, the heat transferred is equal to: A. change in enthalpy B. change in entropy C. change in internal energy D. work nonflow 35. A substance that is able to absorb liquids or gases and is used for removing them from a given medium or region. A. Absorbent B. Cohesive C. Adsorbent D. Adhesive 36. Radiant heat transfer is described by: A. Newton’s law B. Fourier’s law C. The logarithmic mean temperature D. Kirchhoff’s law 37. A reservoir that absorbs energy in the form of heat is called. A. source B. sink C. cold reservoir D. heat reservoir 38. When the entire heat exchanger is selected as control volume, heat becomes. A. unity B. zero C. undefined D. indeterminate 39. Heat is conducted in the direction of: A. increasing temperature B. decreasing temperature C. increasing and decreasing temperature D. constant temperature 40. The heat transfer term in the first law of thermodynamics may be due to any of the following except: A. conduction B. convection C. radiation D. internal heat generation (e.g., chemical reaction) 41. All heat transfer processes require a medium of energy exchange except: A. conduction B. natural convection C. force convection D. radiation 42. Thermal conduction is described by: A. Newton’ law B. The logarithmic mean temperature difference C. The stefan – Boltzmann law D. Fourier’s law 43. Convection is described by which of the following laws? A. Newton’s law B. The logarithmic mean temperature difference C. The Stefan – Boltzmann law D. Fourier’s law 44. Radiation heat transfer is described by A. Newton’s law B. The logarithmic mean temperature difference C. Fourier’s law D. kirchoff’s law 45. The equivalent of ratio of emissive power to absorptivity for bodies in thermal equilibrium is described by: A. Newton’s law B. The logarithmic mean temperature difference C. Fourier’s law D. Kirchoff’s law 46. The temperature potential between temperature at the two ends of a heat exchanger are given by: A. the logarithmic mean temperature difference B. The Stefan-Boltzmann law C. Fourier’s law D. Kirchoff’s law 47. The function of a heat exchanger is to : A. increase the water temperature entering the boiler and decrease combustion requirements B. transfer heat from one fluid to another C. increase the total energy content of the flow D. exchange heat to increase energy to the flow 48. The function of a super heater is to: A. increase the water temperature entering the boiler and decrease combustion requirements B. transfer heat from one fluid to another C. increase the total energy content of the flow D. exchange heat to increase energy to the flow 49. What is the series of processes that eventually bring the system back to its original condition? A. reversible process B. irreversible process C. cycle D. isentropic process 50. A theoretical body which when heated to incandescense would emit a continous light- ray spectrum. A. Black body radiation B. Black body C.Blue body D. White body 51. Which of the following is the reason for insulating the pipes? A. They may not break under pressure B. There is minimum corrosion C. Capacity to withstand pressure D. Heat loss from the is minimized 52. heat transfer due to density differential A. Convection B. Nuclear C. Conduction D. Radiation 53. The term “exposure” in radiological effects is used as a measure of a gamma ray or an X-ray field in the surface of an exposed object. Since this radiation produces ionization of the air surrounding the object, the exposure is obtained as A. number of ions produced per mass of air x coulombs per kg B. mass of air x surface area of an exposed object C. Mass of air over surface area of an exposed object D. number of ions produced per mass of air + coulombs per kg 54. The passing of heat energy from molecule to molecule through a substance A. conduction B. radiation C. conservation D. convection 55. The radiant heat transfer depends on: A. Temperature B. heat rays C. heat flow from cold to hot D. humidity 56. What kind of heat exchanger where water is heated to a point that dissolved gases are liberated? A. Evaporator B. Condenser C. Intercooler D. Deaerator 57. Heat transfer processes which include a change of phase of a fluid are considered. A. convection B. thermal radiation C. conduction D. radiation 58. A hot block is cooled by blowing cool air its top surface. The heat is first transferred to the air layer close to the block is by conduction. It is eventually carried away from the surface by A. convection B. radiation C. conduction D. thermal radiation 59. A body that is hot compared to its surroundings illuminates more energy than it receives, while its surrounding absorbs more energy than they give. The heat is transferred from one to another by energy wave motion. What is this mode of heat transfer? A. Radiation B. Conduction C. Convection D. Condensation 60. What is the heat transfer due to density differential? A. Convection B. Conduction C. Nuclear D. Radiation 61. What do you call the passing of heat energy from molecule to molecule through a substance? A. Conduction B. Conservation C. Radiation D. Convection 62. The transmission of heat from one place to another by fluid circulation between the spots of different temperatures is called. A. Convection B. Conversation C. Radiation D. Conduction 63. Which of the following requires the greatest amount of heat per kilogram for a given increase in temperature? A. Ice B. Water C. Steam D. Copper 64. What do you call the effectiveness of a body as a thermal radiator at a given temperature? A. Absorptivity B. Conductivity C. Emissivity D. Reflectivity 65. The natural direction of the heat flow between two reservoirs is dependent on which of the following? A. Their temperature difference B. Their internal energy C. Their pressures D. Their state, whether solid, liquid ad gas 66. Why are metals good conductors of heat? A. Because they contain free electrons B. Because their atoms are relatively far apart C. Because their atoms are electrons D. Because they have reflecting surfaces 67. In natural convection a heated portion of a fluids moves because: A. its molecular motions becomes aligned B. of molecular collisions within it C. its density is less than that of the sorrounding fluid D. of current in the surrounding fluid 68. In order to emit electromagnetic radiation , an object must be at a temperature: A. above O ˚K B. above O ˚C C. above that of its surrounding D. high enough for it to glow 69. The rate at which an object radiates electromagnetic energy does not depend on its: A. surface area B. mass C. temperature D. ability to absorb radiation 70. sublimation refers to: A. the vaporization of a solid without first becoming liquid B. the melting of a solid C. the vaporization of a liquid D. the condensation of a gas into liquid 71. In the process of freeze dying, ice goes directly into water vapor. What is the temperature at which this process can take place? A. Below the triple point of water B. At the triple point of water C. Above the triple point of water D. Any of the above, depending on the pressure 72. What usually happen when a vapor condenses into a liquid? A. It evolves heat B. it generates heat C. its temperature increase D. It boils with temperature less than 100 ˚C 73. In a cooling tower, the water is cooled mainly by: A. condensation B. convection C. evaporation D. conduction 74. How do you classify a body that has an emissitivity factor of 0.7? A. Gray body B. Black body C. White body D. Theoretical body 75. At what particular condition that no more heat can that be removed from a substance and the temperature can no longer be lowered? A. Freezing point B. Absolute zero C. Critical point D. Ground zero 76. What refers to the heat transfer wherein the heat is transferred from one point to another by actual movement of substance? A. Conduction B. Radiation C. Convection D. Absorption 77. The ratio of the radiation of actual body to the radiation of a blackbody is known as. A. emittance B. reflectance C. absorptance D. transmittance 78. Which of the following is the usual geometric view factor for a black body? A. Zero B. Infinity C. One D. Indeterminate 79. What happens to the heat transferred radially across insulated pipe per unit area? A. The heat will flow at constant rate. B. Decreases with the increase in thermal conductivity C. Decreases from pipe wall to insulated surface D. Partically increases from pipe wall to insulated surface. 80. What do you call a change of phase directly from vapor to solid without passing though the liquid state? A. Sublimation B. Solidification C. Vaporization D. Deposition 81. Which of the following is the Stefan-Boltzmann constant? A. 5.77 x 10 W/m K B. 7.67 x 10 W/m K C. 4.78 x 10 W/m K D. 5.67 x 10 W/m K 82. What is the usual value of transmissivity for opaque materials? A. 0 B.Indetermine C. 1 D. Infinity 83. A body whose emessivity is less than 1 is known as a real body. What is the other term for real body? A. Gray body B. White body C. Black body D. Theoretical body 84. What refers to an ideal body that absorbs all of the radiants energy that introduces on it and also emits the maximum possible energy when acting as a source? A. White body B. Black body C. Gray body D. Red hot body 85. The thermal resistance for one-dimensional steady conduction heat transfer though cylindrical wall in the radial dicrection is expressed in which of the following functions? A. Linear B. Exponetial C. Logarithmic D. Trigonometric 86. The law which states that “the ratio of the emessive powers to absoptivities are equal when the two bodies are in thermal equilibrium is known as: A. Stefan-Boltzmann Law B. Newton’s Law of Convection C. Fourier’s Law D. Kirchhoff’s Law of Radiation 87. It refers to the ratio of the internal thermal resistance of a solid to the boundary layer thermal resistance (or external resistance of the body). A. Biot number B. Prandtl number C. Nusselt number D. Reynolds number 88. It refers to the ratio of the rate of heat transferred by conduction to the rate of energy stored. A. Reynolds number B. Fourier number C. Biot number D. Prandtl number 89. A hot block is cooled by blowing cool air over its top surface. The heat that is first transferred to the air layer close to the block is conduction. It is eventually carrier away from the surface by: A. conduction B. radiation C. thermal D. convection 90. It is the term used to describe the energy of a body that can be transmitted in the form of heat. A. Enthalpy B. Thermal energy C. Entropy D. Internal energy 91. Which of the following is the equivalent heat transferred a gas undergoing isometric process? A. Change in enthalpy B. Change in entropy C. Change in internal energy D. Work nonflow 92. What do you call a substance that is able to absorb liquids or gases and is usually used for removing liquid (or gases) from a given medium or region? A. Absorbent B. liquifier C.Adsorbent D.Adhesive 93. In which direction that heat is transferred through conduction? A. Increasing temperature B. Decreasing temperature C. Increasing and decreasing temperature D. Constant temperature 94. Which of the following statements is based on Prevost theory of heat exchange? A. All bodies above absolute zero emit radiation B. The substance moves because of the decrease in its density which is caused by increase in temperature C. The substance moves because of the application of mechanical power such as that of a fan D. Heat transfer in most of the cases occurs by combinaton of conduction, convection and radiaton 95. Which of the following is the emissivity of white body? A. zero B. 0.5 C. 1 D. 0 < e < 1 96. The mechanism of heat transfer in which there is no medium ( i.e. water, air, solid concrete ) required for the heat energy to travel is: A. Conduction B. Radiation C. Convection D. Diffusion 97. The temperature potential between temperature at the two ends of a heat exchanger are given by: A. the logarithmic mean temperature difference B. the Stefan-Boltzmann law C. Fourier’s law D. Kirchoff’s law 98. Which of the following best describe function of heat exchanger? A. Increase the water temperature entering the system B. Transfer heat from one fluid to another C. Evaluate the total energy content of the flow D. Evaluate heat to increase energy to the flow 99. What refers to a form of energy associated with the kinetic random motion of large numbers of molecules? A. Heat B. Heat of fusion C. Entropy D. Internal energy 100. How much is the part of light that is absorbed by the body that transmits and reflects 80% and 10% respectively? A. 10% B. 30% C. 20% D. 5% 101. In convection heat transfer, what happens to the heat transfer coefficient if the viscosity of the fluid increases? A. The heat transfer coefficient will increase B. The heat transfer coefficient will decrease C. The heat transfer coefficient remains constant D. None of the above 102. How do you call a phenomenon wherein the heat is transferred by motion of fluid under the action of mechanical device? A. Forced convection B. Natural convection C. Forced conduction D. Thermal radiation 103. In conduction heat transfer, what happens to the heat transfer per unit time when the thermal conductivity decreases? A. The heat flow will increase B. The heat flow remains constant C. The heat flow will decrease D. The heat flow will partially increase and then will decrease 104. Which of the following is the driving force in heat transfer? A. Temperature gradient B. Thickness gradient C. Viscosity gradient D. Dielectric gradient 105. Which of the following is the measure of the relative effectiveness of momentum and energy transport by diffusion in the velocity and thermal boundary layer? A. Nusselt’s number B. Prandtl number C. Reynold’s number D. Dimensional measurement 106. Which of the following is the property of the solid that provides the measure of the rate of heat transfer to the energy storage? A. Thermal efficiency B. Thermal diffusivity C. Thermal conductivity D. Thermal radiography 107. Two metals were kept together at room and it was found out that one is colder than the other. Which of the following is the best reason why one metal is colder than the other? A. The heat transfer coefficient of one metal is of higher B. One metal is of lower temperature as compared to the other C. One metal is of higher temperature as compared to the other D. The thermal conductivity of one metal is high as compared to the other 108. In convection heat transfer, what happens to the heat transfer coefficient if the viscosity of the fluid decreases? A. The heat transfer coefficient also increases B. The heat transfer coefficient will decrease C. The heat transfer coefficient remains constant D. The heat transfer coefficient partially increases then decreases 109. A body that is hot compared to its surroundings illuminates more energy than its receives, while its surroundings absorbs more energy than they give. The heat transferred from one to another by energy of wave motion. What is this mode of heat transfer? A. Radiation B. Conduction C. Convection D. Condensation 110. What do you call theoretical body where absorptivity and emissity are independent of the wavelength over the spectral region of the irradiation and the surface emission? A. White body B. Opaque body C. Black body D. Transparent body 111. Which of the following is the structure designed to prevent the spread of fire having a fire resistance rating of not less than four hours? A. Fire escape B. Fire exit C. Fire shield D. Fire wall 112. Which of the following heat exchange device used to provide heat transfer between the exhaust gases and air prior to the entrance of a combustor? A. Regenerator B. Economizer C. Condenser D. Reheater 113. Which of the following transfer of heat is involved in the changing of boiling water (at 100 C ) to vapor at the same temperature? A. Conduction B. Convection C. Radiation D. Evaporation 114. Which of the following is the science of low temperatures? A. Cyrogenics B. Thermo-kinetics C. Themodynamics D. Ergonomics 115. Which of the following thermal state of the body considered as reference to communicate heat to the other bodies? A. Temperature B. Pressure C. Internal energy D. Entropy 116. The true mean temperature difference is also known as: A. the average mean temperature difference B. the logarithmic mean temperature difference C. the trigonometric mean temperature difference D. the exponential temperature difference 117. Which of the following can be a geometric view factor to a gray body? A. Greater than one B. Less than one C. Equal to one D. Greater than zero but less than one 118. The heat transfer by conduction occurs in which of the following ? A. Only in liquids B. Only in solids C. Only in liquids and gases D. In solids, liquids and gases 119. Which of the following reasons why one gram of steam at 100˚C causes more serious burn than 1 gram of water at 100˚C ? A. Steam is less dense than boiling water B. The steam has higher specific heat C. Steam contains more internal energy D. Steam is everywhere thus it strikes greater force 120. What usually happens when vapor condenses into liquid? A. It absorbs heat B. It rejects heat C. Its temperature increases D. Its temperature decreases 121. Which of the following has the highest thermal conductivity? A. Mercury B. Gasoline C. Water D. Alcohol 122. Which of the following is the requirement of the temperature of a body for it to emit radiation? A. Above zero Celsius B. Above zero Kelvin C. Above of the temperature of the surroundings D. High enough for it to glow 123. Which of the following is the color of iron when it is heated to a highest temperature? A. White B. Red C. Orange D. Yellow 124. Which of the following is the reason why metals are good conductors of heat ? A. Metals contain free electrons B. Metals have atoms the frequently collide one another C. Metals have reflecting surfaces D. Atoms in metals are very far to each other 125. The rate at which heat flows through a slab of some material does not depend on which of the following? A. The thickness of the slab B. The area of the slab C. The temperature difference between two faces D. The specific heat of the material 126. Which of the following is the primary function of a thermal radiator? A. To transferring the heat by using moving liquids B. To transfer heat from hot to cold body by using a forced-draft fan C. To transfer heat by allowing molecules to vibrate one to another D. To transfer heat with or without a medium 127. What is the reason why styrofoam is a good insulating material? A. Because it contains many tiny pockets of air B. Styrofoam is a white object C. The structure of styrofoam is very unstable and heat cannot flow D. Styrofoam structure is very dense 128. What usually happens to the surrounding when water vapor condenses? A. It warms the surrounding B. The surrounding temperature decreases C. It neither warm nor cold the surrounding D. The surrounding will be dehumidified 129. The rate of radiation does not depend on which of the following? A. Temperature of the radiating body B. The emissivity of the radiation surface C. The area of the radiating body D. The thickness of the radiating body 130. Which of the following is not a good conductor of heat? A. Metals B. Rocks C. Glass D. Asbestos 131. Which of the following is not a unit of the rate of heat transfer? A. Watt B. Btu per hour C. Cal/s D. Btu/Hp-hr 132. The thermal conductivity does not depend on which of the following? A. Chemical composition B. Physical state or texture C. Temperature and pressure D. Gravitational pull 133. In Maxell’s theory for thermal conductivity of gases and vapors, which of the following is the value of “a” for triatomic gases? A. 1.7 B. 2.4 C. 1.3 D. 2.4 134. Which of the following conductivities where Sutherland equation is used? A. Thermal conductivities of solid B. Thermal conductivities of gases C. Thermal conductivities of metal D. Thermal conductivities of liquids 135. For pure metals, what happens to the thermal conductivity if the temperature is extremely high? A. Approaches infinity B. Decreases except for ferrous metals C. Almost constant except for ferromagnetic materials D. Increases except for steel 136. Which of the following liquids that has the highest thermal conductivity? A. Gasoline B. Glycerin C. Water D. Alcohol 137. Which of the following is not a heat exchanger? A. Condenser B. Boilers C. Evaporators D. Water hammer 138. Which of the following heat exchangers where fluid flow in the same direction and both are of changing temperatures? A. Parallel flow B. Cross flow C. Counter flow D. Mixed flow 139. What happens to the thermal conductivity of diatomic gases if the temperature is increases? A. The thermal conductivity will also increases B. The thermal conductivity decreases C. The thermal conductivity remains constant D. The thermal conductivity partially increases then decreases. 140. What device is used to measure the amount of infrared radiation in each portion of a person’s skin that is emitted? A. Thermograph B. Thermometer C. Pyrometer D. Potentiometer 141. The heat transfer by convection occurs in which of the following? A. Only in gases B. Only in liquids C. Only in gases and liquids D. Only in gases and solids 142. In convection heat transfer, what mechanism heat transfer where the fluid moves due to the decrease in its density caused by increase in temperature? A. Forced convection B. Natural convection C. Density convection D. Radial convection