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1. Refrigerated air conditioning is used in _______________
a. Hot temperature with high humidity
b. Hot temperature with low humidity
c. Hot temperature with high and low humidity
d. None of the above
Explanation: Refrigerated air conditioning systems are designed to handle both sensible heat (temperature) and latent heat (humidity), making them effective in both dry and humid climates. Source: ASHRAE Handbook - HVAC Systems and Equipment.
2. A refrigerated system that cleans, dehydrates, and cools a compartment.
a. No frost refrigerator
b. Chiller
c. Freezer
d. Air conditioner
Explanation: An air conditioning system performs multiple functions simultaneously: it cools the air, dehydrates (dehumidifies) it by condensing moisture over the evaporator coils, and cleans it via air filters. Source: Fundamentals of HVAC.
3. Which of the following statements is true:
a. The motor and compressor of a refrigeration system is separately installed.
b. The motor and compressor of a refrigeration system is housed in the same compartment.
c. The compressor and the motor of a refrigeration system is non-hermitic type?
d. None of the above
Explanation: In modern domestic and light commercial refrigeration, the compressor and its driving electrical motor are sealed within the same welded steel shell, known as a hermetic compressor. Source: Modern Refrigeration and Air Conditioning.
4. The highest pressure in the refrigeration system can be found at _______________
a. The capillary tube
b. The entrance of the evaporator coil
c. The evaporator coil immediately before the compressor
d. None of the above
Explanation: The highest pressure in a refrigeration cycle is found on the "high side," which consists of the compressor discharge line, the condenser, and the liquid line up to the expansion device. The other options listed describe the low-pressure side. Source: Thermodynamics: An Engineering Approach.
5. A refrigeration system component after the condenser.
a. Capillary tube
b. Filter
c. Compressor
d. None of the above
Explanation: Liquid refrigerant leaving the condenser passes through a filter-drier to remove moisture and particulate matter before it reaches the metering device (like a capillary tube). Source: Refrigeration Component Design standards.
6. A refrigeration system component after the capillary tube.
a. Evaporator
b. Compressor
c. Condenser
d. None of the above
Explanation: The capillary tube drops the pressure of the refrigerant, which then directly enters the evaporator to boil and absorb heat. Source: Vapor-Compression Cycle Basics.
7. A refrigeration system component before the condenser.
a. Filter
b. Evaporator
c. Compressor
d. None of the above
Explanation: The compressor takes low-pressure vapor, compresses it into high-pressure vapor, and discharges it directly into the condenser. Source: ASHRAE Refrigeration Handbook.
8. Lowest temperature zone in refrigeration system.
a. Condenser
b. Capillary tube
c. Evaporator
d. None of the above
Explanation: The evaporator operates at the lowest pressure and temperature in the system, allowing heat to flow from the conditioned space into the refrigerant. Source: Principles of Heat Transfer.
9. State of refrigerant at the condenser side immediately after leaving the compressor.
a. Superheated gas
b. Lukewarm liquid
c. Saturated gas
d. None of the above
Explanation: The compression process raises the temperature of the vapor well above its saturation temperature for that given pressure, rendering it a superheated gas. Source: Thermodynamics P-h Diagrams.
10. State of refrigerant at the evaporator side immediately before the compressor.
a. Superheated gas
b. Saturated gas
c. Lukewarm liquid
d. None of the above
Explanation: In a theoretical vapor-compression cycle, the refrigerant exits the evaporator as 100% saturated vapor (gas) before entering the compressor. Source: Fundamentals of Thermodynamics.
11. A newly discovered refrigerant that is not harmful for the ozone layer or referred to as “ozone friendly gas.”
a. R12
b. Ammonia
c. Suva Mp 52 (R-134a)
d. All of the above
Explanation: R-134a (Tetrafluoroethane) is an HFC with an Ozone Depletion Potential (ODP) of zero, introduced specifically to replace ozone-depleting CFCs like R-12. Source: EPA Refrigerant Classifications.
12. It is the term used for the overcharging of refrigerant.
a. Back frost
b. Sweating
c. Supercharging
d. None of the above
Explanation: Overcharging causes liquid refrigerant to flood past the evaporator and boil in the suction line, freezing ambient moisture into "back frost" on the line leading to the compressor. Source: HVAC Troubleshooting guides.
13. It is the term used for overcharging of refrigerant.
a. Back frost
b. Sweating
c. Supercharging
d. None of the above
Explanation: "Frosting back" is a primary visual indicator of an overcharged system or severely restricted airflow over the evaporator. Source: Refrigeration and Air Conditioning Technology.
14. It is a mixture of 1/2 vapor and 1/2 liquid.
a. Saturated gas
b. Saturated liquid
c. Superheated gas
d. None of the above
Explanation: A state containing both liquid and vapor at equilibrium exists within the vapor dome as a two-phase saturated mixture. Source: Thermodynamics Principles.
15. It is a mixture of 1/2 liquid and 1/2 gas.
a. Saturated gas
b. Saturated liquid
c. Superheated gas
d. None of the above
Explanation: A state containing both liquid and vapor at equilibrium exists within the vapor dome as a two-phase saturated mixture. Source: Thermodynamics Principles.
16. Charging pressure for refrigerator and freezer using R-12 refrigerant.
a. 19 psi
b. 65 psi
c. 75 psi
d. None of the above
Explanation: For low-temperature refrigeration applications (freezers operating near 0ºF / -18ºC), the low-side suction pressure for R-12 is typically between 10 to 19 psig. Source: P-T charts for R-12.
17. Larger floor area for the same height of wall use light _________
a. More efficiently than rooms with smaller floor area
b. Less efficiently than rooms with smaller floor area
c. The same with smaller rooms
d. None of the above
Explanation: In lighting design, larger rooms have a higher Room Cavity Ratio (RCR) efficiency because a smaller percentage of the emitted light strikes the walls and gets absorbed. Source: IESNA Lighting Handbook.
18. Charging pressure for air conditioning unit using R-12 refrigerant.
a. 19-45 psi
b. 65-75 psi
c. 80-90 psi
d. None of the above
Explanation: Air conditioning systems operate at higher evaporator temperatures (approx. 40ºF) compared to freezers. For R-12, this corresponds to a suction pressure of roughly 65-75 psi. Source: ASHRAE Refrigerant Data.
19. A dry ice is ______________
a. Solid H2O
b. Solid CO2
c. Solid O2
d. None of the above
Explanation: Dry ice is the common name for the solid form of carbon dioxide (CO2). It sublimates directly from a solid to a gas at -78.5°C. Source: General Chemistry.
20. A device used mostly in larger cooling units to cool the water that absorbs the heat from the condenser.
a. Cold storage room
b. Cooling Tower
c. Heat Exchanger
d. None of the above
Explanation: A cooling tower rejects heat from water-cooled chillers into the atmosphere by evaporating a small portion of the circulating water. Source: HVAC Systems Design.
21. When a condenser of a refrigeration system is cooling what is the common trouble?
a. Too much refrigerant
b. Lacks refrigerant
c. No refrigerant
d. None of the above
Explanation: A lack of refrigerant (undercharge) prevents the system from having enough fluid to effectively transfer and reject heat at the condenser, resulting in a cooler-than-normal condenser and poor overall cooling performance. Source: Refrigeration Service Engineering Society (RSES).
22. It is the passage of from the outside of a leaky room cause by cracks in windows, doors, and other possible sources.
a. Heat loss
b. Air infiltration
c. Air gap
d. None of the above
Explanation: Infiltration is the uncontrolled leakage of unconditioned outdoor air into a building through gaps, increasing the heating or cooling load. Source: ASHRAE Fundamentals - Ventilation and Infiltration.
23. Known as Dichlorodifluoromethane used as primary refrigerant for refrigerator.
a. R-11
b. R-12
c. R-22
d. None of the above
Explanation: R-12 (Freon-12) is the chemical dichlorodifluoromethane. It was the standard refrigerant for domestic refrigeration before being phased out. Source: EPA Phase-out of CFCs.
24. Known as Monochlorodifluoromethane used a primary refrigerant for aircon systems.
a. R-11
b. R-12
c. R-22
d. None of the above
Explanation: R-22 (Freon-22) is chlorodifluoromethane. It was the dominant refrigerant for residential and commercial air conditioning systems for decades. Source: EPA Refrigerant Listings.
25. The transfer of heat from one part of a solid body to the other under the influence of temperature gradient.
a. Convection
b. Conduction
c. Radiation
d. All of the above
Explanation: Conduction is the mode of heat transfer across a stationary medium (solid or fluid) due to the random motion and collisions of atoms and molecules. Source: Heat and Mass Transfer Fundamentals.
26. The transfer of heat by mixing one parcel of fluid with another.
a. Convection
b. Conduction
c. All of the above
d. None of the above
Explanation: Convection involves the macroscopic movement of a fluid. Heat is transferred as warmer, less dense fluid mixes with cooler fluid. Source: Fluid Mechanics and Heat Transfer.
27. Shape factor for heat by conduction is expressed as
a. A/dx
b. K A/dx
c. dt/dx
d. None of the above
Explanation: In Fourier's law of conduction, the shape factor for a simple plane wall of area A and thickness dx is A/dx. Source: Heat Transfer Engineering.
28. It is the amount of heat transferred per unit temperature per unit length.
a. Emissivity
b. Thermal conductivity
c. Heat transfer coefficient
d. None of the above
Explanation: Thermal conductivity defines a material's inherent ability to conduct heat, measured in W/m·K. Source: Material Science and Heat Transfer.
29. When heat is transmitted through molecular waves, it is transmitted by ___________
a. Convection
b. Conduction
c. Radiation
d. None of the above
Explanation: Thermal radiation is energy emitted by matter as electromagnetic waves. Unlike conduction and convection, it does not require a physical medium. Source: Physics of Heat.
30. The amount of heat required to raise one pound of water one degree Fahrenheit.
a. Thermal capacity
b. Specific heat
c. British thermal unit
d. None of the above
Explanation: The British Thermal Unit (BTU) is defined as the heat energy required to raise the temperature of 1 pound of liquid water by 1ºF. Source: Standard Imperial Thermodynamics units.
31. It is a proportionality factor that represents the property of material through heat conduction.
a. Thermal resistivity
b. Thermal conductivity
c. Thermal coefficient
d. None of the above
Explanation: In Fourier's Law, the constant of proportionality is the thermal conductivity of the specific material. Source: Fourier's Law of Heat Conduction.
32. Cooling meat, fruits and vegetables are examples of heat transmission by ___________
a. Unsteady state conduction
b. Steady state conduction
c. Free convection
d. None of the above
Explanation: Because the temperature of the food product is constantly changing (cooling down over time) rather than remaining constant, it is a transient or unsteady state heat transfer process. Source: Food Engineering principles.
33. Factors influencing thermal conductivity.
a. Chemical composition of materials
b. Temperature of materials
c. Surrounding pressure
d. All of the above
Explanation: Thermal conductivity is highly dependent on the phase and chemical composition of a substance, its internal temperature, and the ambient pressure. Source: CRC Handbook of Chemistry and Physics.
34. If the temperature surrounding the material is decreased, the thermal conductivity also _____
a. Changes in decreasing manner
b. Changes in increasing manner
c. Does not change
d. None of the above
Explanation: For most gases and insulating non-metallic liquids/solids, thermal conductivity decreases as temperature decreases due to reduced molecular kinetic energy. Source: Heat Transfer textbooks.
35. The transfer of heat from one part of a solid body to the other under the influence of temperature gradient.
a. Convection
b. Conduction
c. Radiation
d. All of the above
Explanation: Conduction is the mode of heat transfer across a stationary medium due to the random motion and collisions of atoms and molecules. Source: Heat and Mass Transfer Fundamentals.
36. The transfer of heat from mixing one parcel of fluid with another.
a. Convection
b. Conduction
c. Radiation
d. All of the above
Explanation: Convection involves the macroscopic movement of a fluid. Heat is transferred as warmer, less dense fluid mixes with cooler fluid. Source: Fluid Mechanics and Heat Transfer.
37. Shape factor for heat by conduction is expressed as ___________
a. A/dx
b. K A/dx
c. dt/dx
d. None of the above
Explanation: In Fourier's law of conduction, the shape factor for a simple plane wall of area A and thickness dx is A/dx. Source: Heat Transfer Engineering.
38. It is the amount of heat transferred per unit temperature per unit length.
a. Emissivity
b. Thermal conductivity
c. Heat transfer coefficient
d. None of the above
Explanation: Thermal conductivity defines a material's inherent ability to conduct heat, measured in W/m·K. Source: Material Science and Heat Transfer.
39. When heat is transmitted through molecular waves, it is transmitted by_____________
a. Convection
b. Conduction
c. Radiation
d. None of the above
Explanation: Thermal radiation is energy emitted by matter as electromagnetic waves. Unlike conduction and convection, it does not require a physical medium. Source: Physics of Heat.
40. The amount of heat required to raise one pound of water on degree Fahrenheit.
a. Thermal capacity
b. Specific heat
c. British Thermal unit
d. None of the above
Explanation: The British Thermal Unit (BTU) is defined as the heat energy required to raise the temperature of 1 pound of liquid water by 1ºF. Source: Standard Imperial Thermodynamics units.
41. It is a proportionality factor that represents the property of material through heat conduction.
a. Thermal resistivity
b. Thermal conductivity
c. Thermal coefficient
d. None of the above
Explanation: In Fourier's Law, the constant of proportionality is the thermal conductivity of the specific material. Source: Fourier's Law of Heat Conduction.
42. Cooling meat, fruits and vegetables are example of heat transmission by _________
a. Unsteady state conduction
b. Steady state conduction
c. Free convection
d. None of the above
Explanation: Because the temperature of the food product is constantly changing (cooling down over time) rather than remaining constant, it is a transient or unsteady state heat transfer process. Source: Food Engineering principles.
43. Factors influencing thermal conductivity.
a. Chemical composition of materials
b. Temperature of materials
c. Surrounding pressure
d. All of the above
Explanation: Thermal conductivity is highly dependent on the phase and chemical composition of a substance, its internal temperature, and the ambient pressure. Source: CRC Handbook of Chemistry and Physics.
44. If the temperature surrounding the material is decrease, the thermal conductivity also ______
a. Changes in decreasing manner
b. Changes in increasing manner
c. Does not change
d. None of the above
Explanation: For most gases and insulating non-metallic liquids/solids, thermal conductivity decreases as temperature decreases due to reduced molecular kinetic energy. Source: Heat Transfer textbooks.
45. Fluids with low molecular weight have _______________
a. High thermal conductivity
b. Low thermal conductivity
c. No thermal conductivity
d. None of the above
Explanation: Lighter molecules (like Hydrogen and Helium) move faster at a given temperature, facilitating more rapid collisions and thus higher thermal conductivity than heavier fluids. Source: Kinetic Theory of Gases.
46. Heat basically transfer from _____________
a. Lower temperature to high temperature
b. High temperature to lower temperature
c. Lower pressure to higher pressure
d. None of the above
Explanation: According to the Second Law of Thermodynamics (Clausius statement), thermal energy spontaneously flows from a region of higher temperature to one of lower temperature. Source: Principles of Thermodynamics.
47. If more heat is to be transmitted from one side to the other side of a solid body, what would you recommend as an engineer?
a. Increase the thickness of material
b. Decrease the thickness of material
c. Maintain the thickness of material
d. None of the above
Explanation: Because heat transfer rate is inversely proportional to thickness in Fourier's Law, decreasing the thickness reduces thermal resistance and increases heat flow. Source: Heat and Mass Transfer Fundamentals.
48. The shape factor for conduction heating on a cylindrical wall is _____________
a. 6.3 L/In r 2/rl
b. 3.14L/In r 2/rl
c. 3.14 kL/In r 2/rl
d. None of the above
Explanation: The exact formula for radial conduction shape factor is 2Ï€L / ln(r2/r1). Since 2Ï€ is approximately 6.28, "6.3 L / ln(r2/r1)" is the closest mathematical approximation. Source: Conduction Heat Transfer Geometry.
49. The amount of heat transmitted per unit time and temperature for a given surface area by a fluid.
a. Heat coefficient
b. Specific heat
c. Heat transfer coefficient
d. None of the above
Explanation: The convective heat transfer coefficient (h), used in Newton's Law of Cooling, represents the rate of heat transfer per unit area per unit temperature difference. Source: Fluid/Thermal Engineering.
50. If a boiling water is pumped from a boiler to a heat exchanger, heat is transmitted by ______
a. Natural convection
b. Forced convection
c. Radiation
d. None of the above
Explanation: Because the fluid (water) is being moved mechanically via a pump rather than relying purely on buoyancy/density differences, the convective heat transfer is classified as "forced." Source: Thermodynamics and Fluid Mechanics.
51. Heat transfer coefficient is lower for __________
a. Liquids
b. Gases
c. Boiling water
d. None of the above
Explanation: Gases possess lower thermal conductivity and much lower density compared to liquids, which inherently results in a lower convective heat transfer coefficient. Source: Fundamentals of Heat and Mass Transfer.
52. An example of a heat conductor.
a. Silica brick
b. Refractory cement
c. Asbestos fiber
d. None of the above
Explanation: Silica brick, refractory cement, and asbestos are all highly rated thermal insulators (or refractories) designed to resist heat flow. Metals like copper or aluminum would be examples of heat conductors. Source: Materials Science and Engineering.
53. In a vacuum condition, heat transfer by conduction moves __________
a. Faster
b. Slower
c. At a constant rate
d. None of the above
Explanation: Conduction strictly requires a physical medium (particles and molecules) to transfer thermal energy. In a vacuum, where no physical medium exists, conduction halts completely. Source: Principles of Heat Transfer.
54. In sun drying, heat is released from a body primarily by ________________
a. Radiation
b. Forced convection
c. Natural convection
d. None of the above
Explanation: While a body receives heat via solar radiation, the moisture and heat from the drying agricultural product are released back into the surrounding environment primarily through natural convection and evaporation. Source: Agricultural Process Engineering.
55. The amount of heat required to raise a kilogram of water one degree centigrade.
a. Kilo calories
b. Joules
c. Watts
d. None of the above
Explanation: A kilocalorie (or large calorie) is thermodynamically defined as the amount of heat energy required to raise the temperature of one kilogram of water by 1°C. Source: Standard Thermodynamics Definitions.
56. Dimensionless numbers used in determining heat transfer coefficient by natural convection.
a. Nusselt / Grashof / Prandtl
b. Nusselt / Reynolds / Prandtl
c. Prandtl / Reynolds / Grashof
d. None of the above
Explanation: In natural (free) convection, the Nusselt number is correlated as a function of the Grashof and Prandtl numbers. The Reynolds number is applied specifically to forced convection. Source: Heat and Mass Transfer Fundamentals.
57. The unit of energy in the SI system is ___________
a. Newton-meter
b. Joules
c. Watt-second
d. All of the above
Explanation: In the International System of Units (SI), the base unit of energy is the Joule (J). One Joule is exactly equivalent to one Newton-meter (N·m) of work or one Watt-second (W·s) of electrical energy. Source: SI Unit Standards.
58. It is the insulating ability of a material or the resistance of a material to the flow of heat.
a. Thermal resistance
b. Thermal conductivity
c. Thermal insulator
d. All of the above
Explanation: Thermal resistance (often quantified as R-value) is the specific property indicating how strongly a material or structural component resists the conductive flow of heat. Source: ASHRAE Fundamentals.
59. The property that dictates the ability of a body to give up or to receive heat.
a. Heat
b. Temperature
c. Energy
d. All of the above
Explanation: Temperature is the intensive property that dictates the direction of heat transfer; thermal energy will inherently flow from a body with a higher temperature to a body with a lower temperature. Source: Second Law of Thermodynamics.
60. To protect external insulation from environmental and mechanical damage, the insulate must be provided with protective __________
a. Metal sheet cladding
b. Nets and asbestos cement
c. Wire net and bituminous compound
d. All of the above
Explanation: Insulation materials themselves are frequently fragile or porous. They must be jacketed, clad with aluminum or stainless steel sheets, or sealed with reinforced cements and mastic compounds to protect against weather, moisture intrusion, and mechanical impact. Source: Industrial Insulation Practices.
61. The Stefan-Boltzmann constant in Imperial units is approximately equal to ______________
a. 0.147 x 10^-8 BTU/hr-ft^2-R^4
b. 0.1714 x 10^-8 BTU/hr-ft^2-R^4
c. 0.174 x 10^-8 BTU/hr-ft^2-R^3
d. None of the above
Explanation: In standard Imperial thermodynamic units, the physical constant of proportionality known as the Stefan-Boltzmann constant (σ) is evaluated at approximately 0.1714 × 10^-8 BTU / (hr·ft²·°R⁴). Source: Standard Thermodynamics Reference Tables.
62. The equation for total heat transfer by radiation for non-ideal "gray bodies" is __________
a. Qr = σ A T^4
b. Qr = ε σ A T^4
c. Or = ε σ A T^3
d. None of the above
Explanation: The standard Stefan-Boltzmann law dictates ideal black body radiation. For real-world gray bodies, the equation scales down total radiation by incorporating the surface's emissivity (ε), yielding Q_rad = ε σ A T^4. Source: Heat Transfer Fundamentals.
63. It is an engineered device constructed exclusively for transferring thermal heat between fluids.
a. Insulator
b. Heat absorber
c. Heat exchanger
d. All of the above
Explanation: A heat exchanger is a specialized thermodynamics device built specifically to efficiently transfer sensible or latent thermal energy from one process fluid to another, typically separated by a solid barrier. Source: Thermodynamics and Fluid Systems.
64. The overall heat transfer coefficient incorporates _______________
a. Thermal conductivity and the heat transfer coefficients of the boundary materials
b. Heat transfer coefficient and emissivity of the materials
c. Thermal conductivity and emissivity of the materials
d. None of the above
Explanation: The overall heat transfer coefficient (U-value) is a composite value that aggregates the convective heat transfer coefficients (h) of the fluid layers on both sides of a barrier and the conductive thermal resistance (k) of the dividing wall itself. Source: Heat and Mass Transfer.
65. Which of the following laws of optics and thermal radiation is true?
a. When radiant energy falls on a body, part may be reflected, part absorbed, and the remainder transmitted.
b. When radiant falls on a body, all of the energy is strictly absorbed.
c. When radiant energy falls on a body, part may only be reflected and absorbed.
d. None of the above
Explanation: By conservation of energy and principles of thermal radiation, the total incident radiant energy upon a surface equals the strict sum of the energy that is absorbed, reflected, and transmitted through the body. Source: Planck's and Kirchhoff's Radiation Laws.
66. When two separated fluids in a heat exchanger move in exactly opposite directions, the device configuration is classified as.
a. Parallel flow HE
b. Cross flow HE
c. Constant flow HE
d. None of the above
Explanation: When fluids move in entirely opposite directions, the design is classified as a counter-flow (or counter-current) heat exchanger. Because this classification is not listed in the standard options, "None of the above" is the correct choice. Source: Heat Exchanger Design Fundamentals.
67. The radiation configuration factor (view factor) for infinite parallel planes in calculating heat exchanged is
a. Higher than perpendicular planes
b. Lower for perpendicular planes
c. Equal to perpendicular planes
d. All of the above
Explanation: The geometric view factor between two directly opposing infinite parallel planes approaches 1.0 (the maximum possible radiation capture), which is fundamentally higher than planes positioned perpendicularly to one another. Source: Radiation Heat Transfer View Factors.
68. It is a composite mixture of cement, gravel, sand and water that cures and hardens to the shape and dimension of the desired structure.
a. Bricks
b. Masonry
c. Concrete
d. All of the above
Explanation: Concrete is a foundational engineering composite building material created by mixing aggregate (sand and coarse gravel), a binder (cement), and water, which undergoes an exothermic hydration process to harden over time. Source: Civil Engineering Materials.
69. It is a pre-construction project analysis determining the precise quality, quantity, and cost of every material required in the finished work.
a. Feasibility study
b. Project planning
c. Estimate
d. None of the above
Explanation: A structural estimate (or material quantity take-off) is the rigorous process of calculating the specific material volumes, labor hours, and costs required to fully construct a project based directly on its design drawings. Source: Construction Project Management.
70. Temperature of the surrounding air.
a. Dry bulb temperature
b. Wet bulb temperature
c. Ambient temperature
d. All of the above
Explanation: Ambient temperature strictly refers to the general temperature of the surrounding air or immediate environment around a subject or piece of equipment. Source: HVAC and Refrigeration Terminology.
71. It is the form of energy that moves due to a difference in temperature.
a. Heat
b. Temperature
c. Thermal resistance
d. None of the above
Explanation: Heat is defined as thermal energy in transit strictly due to a spatial temperature difference between two regions or systems. Source: Fundamentals of Heat Transfer.
72. Nusselt number is a function of __________
a. Convection coefficient, characteristic length (pipe diameter), and thermal conductivity
b. Thermal conductivity, viscosity, and diameter of pipe
c. Convection coefficient, velocity of fluid, diameter of pipe
d. None of the above
Explanation: The Nusselt number (Nu) represents the ratio of convective to conductive heat transfer, defined as Nu = hL/k, where 'h' is the convective heat transfer coefficient, 'L' is the characteristic length, and 'k' is the fluid's thermal conductivity. Source: Fluid Mechanics and Heat Transfer.
73. A thick wall tube of stainless steel (k = 19 W/m-C) with 2 cm ID and 4 cm OD. If the inside wall temperature of the pipe is maintained at 600 C and the outside of the insulation at 100 C, what is the heat loss per meter length of the tube?
a. 600 W/m
b. 680 W/m
c. 720 W/m
d. None of the above
Explanation: The rate of steady-state radial heat conduction through a cylindrical wall is calculated using Fourier's law for cylinders: q/L = 2Ï€k(T_inside - T_outside) / ln(r_outer/r_inner). Source: Heat Transfer Calculations.
74. Which of the following has the highest heat transfer coefficient?
a. Gases
b. Liquids
c. Boiling water
d. All of the above
Explanation: Phase change processes, such as boiling or condensation, involve massive exchanges of latent heat, yielding convective heat transfer coefficients orders of magnitude higher than single-phase liquids or gases. Source: Fundamentals of Heat and Mass Transfer.
75. The free convection heat transfer coefficient of liquid in kcal/m²-hr-C is generally in the range of _____________
a. 3 to 20
b. 100 to 600
c. 1000 to 2000
d. None of the above
Explanation: Natural (free) convection for liquids typically ranges from 100 to 600 kcal/m²-hr-C, which is significantly higher than free convection in gases (3 to 20) but lower than boiling phase changes. Source: Chemical Engineering Fluid Mechanics and Heat Transfer Data.
76. Which of the following is true regarding thermal conductivity?
a. The thermal conductivity of aluminum is higher than silver
b. Silver transmits heat faster than aluminum
c. Aluminum and silver transfer heat at the same rate
d. All of the above
Explanation: Silver possesses one of the highest thermal conductivities of any pure metal (approx. 429 W/m·K), making it a much faster transmitter of heat than aluminum (approx. 237 W/m·K). Source: CRC Handbook of Chemistry and Physics.
77. What is the total board feet of 5 pieces of 2 in x 6 in x 14 feet wood?
a. 50 bd ft
b. 60 bd ft
c. 70 bd ft
d. None of the above
Explanation: Board feet is calculated using the formula: (Thickness in inches × Width in inches × Length in feet) / 12. For 5 pieces: 5 × (2 × 6 × 14) / 12 = 70 board feet. Source: Agricultural Engineering Standard Formulas.
78. What is the heat loss per ft² of a brick kiln wall 9-inches thick made of a material with a thermal conductivity of 0.18 BTU/hr-ft-F? The outside and inside temperatures are 1500 F and 400 F, respectively.
a. 224 BTU/hr-ft²
b. 264 BTU/hr-ft²
c. 246 BTU/hr-ft²
d. None of the above
Explanation: Using Fourier's Law of steady-state 1D Conduction (q/A = k × Î”T / x). The thickness must be in feet (9/12 = 0.75 ft). Therefore, q/A = 0.18 × (1500 - 400) / 0.75 = 264 BTU/hr-ft². Source: Heat Transfer Calculations.
79. What is the heat transfer loss per foot of a 2-inch nominal pipe (OD=2.37 in) covered with 1-in. thick insulating material having an average thermal conductivity of 0.037 BTU/hr-ft-F? The inner and outer temperatures of the insulation are 380 F and 80 F, respectively.
a. 161 BTU/hr-ft
b. 111 BTU/hr-ft
c. 125 BTU/hr-ft
d. None of the above
Explanation: Calculated using the radial heat conduction formula for a cylinder: q/L = 2Ï€k(T1 - T2) / ln(r2/r1). The inner radius of the insulation is half the pipe OD (1.185 in), and outer radius is r1 + 1 in (2.185 in). Evaluating yields approximately 114 BTU/hr-ft, making 111 the closest approximation option provided. Source: Heat Transfer Engineering.
80. The Prandtl number is a function of ______________
a. Viscosity, specific heat, and thermal conductivity
b. Specific heat, heat transfer coefficient, and thermal conductivity
c. Viscosity, diameter of pipe, thermal conductivity
d. None of the above
Explanation: The Prandtl number (Pr) is the dimensionless ratio of momentum diffusivity to thermal diffusivity, defined as Pr = (Cp × Î¼) / k, where Cp is specific heat, μ is dynamic viscosity, and k is thermal conductivity. Source: Fluid Mechanics and Heat Transfer.
81. Heat transfer coefficient by forced convection is determined by what dimensionless numbers?
a. Nusselt, Prandtl, Reynolds
b. Nusselt, Prandtl, Grashof
c. Reynolds, Grashof, Prandtl
d. None of the above
Explanation: In forced convection, the Nusselt number (which correlates to the heat transfer coefficient) is expressed as an empirical function of the Reynolds number (representing flow characteristics) and the Prandtl number (representing fluid properties). Source: Fundamentals of Heat and Mass Transfer.
82. One British thermal unit is equal to ______________
a. 1055 J
b. 1505 J
c. 1550 J
d. None of the above
Explanation: The International Table British Thermal Unit (BTU) is precisely defined in thermodynamic tables as 1,055.056 Joules. Source: NIST Unit Conversions.
83. If the heated pipe is changed to a higher pipe schedule, the internal conductive heat transfer rate will ________
a. Increase
b. Decrease
c. Remain the same
d. All of the above
Explanation: A higher pipe schedule designates a thicker pipe wall. Increased wall thickness increases radial thermal resistance, thereby decreasing the rate of conductive heat transfer through the wall. Source: Piping Engineering and Thermodynamics.
84. Basically, the thermal conductivity of a gaseous material will increase if the ______________
a. Thickness is increased
b. Temperature is increased
c. Temperature is decreased
d. All of the above
Explanation: For gases and some non-metallic solids, thermal conductivity increases as temperature increases due to higher molecular kinetic energy and velocity resulting in faster thermal transport. Source: Thermodynamics and Material Science.
85. Which of the following statements regarding 3D structural heat transfer is generally true?
a. Heat transfer rate is uniform across all surfaces.
b. Heat transfer rate is highest on corners of boxes.
c. Heat transfer rate is lower on the walls of boxes.
d. None of the above
Explanation: In 3D conduction geometries, corners act as thermal bridges where three intersecting planes meet. The external surface area is significantly larger than the internal area, resulting in a higher concentrated outward heat flux. Source: Building Physics and Thermal Bridging.
86. Which of the following statements regarding poultry waste is true?
a. Layers produce more manure per lifespan than broilers
b. Broilers produce more manure per day than layers
c. Both produce the same amount of manure per day
d. None of the above
Explanation: Because layer hens are kept significantly longer (often over a year for egg production), they generate a much higher cumulative volume of manure compared to broilers, which are typically harvested at around 6 weeks of age. Source: Philippine Agricultural Engineering Standards (PAES) - Poultry Housing.
87. A good insulator for a kiln dryer.
a. Rice husk
b. Brick (Refractory)
c. Concrete
d. None of the above
Explanation: Firebricks or refractory bricks are traditionally used in kiln dryers because they can structurally withstand internal high temperatures while providing adequate thermal insulation to reduce heat loss. Source: Agricultural Process Engineering.
88. A material which is a poor conductor of heat or has low thermal conductivity.
a. Conductor
b. Insulator
c. Resistor
d. All of the above
Explanation: Thermal insulators are specifically engineered materials selected because they possess very low thermal conductivity, thereby strongly resisting the flow of heat. Source: Materials Science.
89. A historical example of a good insulating material at extremely high temperatures.
a. Iron
b. Wood
c. Asbestos
d. All of the above
Explanation: Asbestos was historically relied upon heavily for high-temperature industrial insulation due to its excellent thermal resistance and fireproof properties, though it is largely phased out today due to health hazards. Source: Industrial Insulation Materials.
90. Which of the following has the lowest thermal conductivity?
a. Building brick
b. Asbestos
c. Firebrick
d. Concrete
Explanation: Asbestos has a much lower thermal conductivity (making it a highly effective insulator) compared to denser structural construction materials like concrete, building brick, and firebrick. Source: Heat Transfer Material Property Tables.
91. Insulators used for steam lines are generally classified into __________
a. Low temperature range insulator
b. Medium temperature range insulator
c. High temperature range insulator
d. None of the above
Explanation: Depending on the industrial classification standards, steam line insulators are categorized in the medium to high-temperature range to handle saturated and superheated steam temperatures safely without degradation. Source: ASHRAE Systems and Equipment.
92. A good example of a dual temperature insulator (capable of handling both hot and cold).
a. Expanded silica
b. Cellular glass
c. Vermiculite
d. All of the above
Explanation: Cellular glass (foam glass) is highly regarded as a dual-temperature insulator because it is completely impermeable to moisture and vapor drive, making it perfectly effective for both hot applications and sub-ambient (cold) lines without the risk of condensation freezing inside the insulation. Source: Insulation Institute Guidelines.
93. Forms of insulation used in industrial insulation practice.
a. Flexible strips
b. Foil
c. Flexible pipe sections and mattresses
d. All of the above
Explanation: Industrial insulation utilizes various forms depending on the geometry and requirements of the application, including rigid boards, flexible strips, pre-formed pipe sections, reflective foils, and insulating mattresses for complex valves. Source: Industrial Insulation Practice Manuals.
94. Which of the following statements regarding the economics of insulation is true?
a. In insulation, heat gain is more costly than heat loss
b. The cost of extracting heat from a refrigerated space is the same as generating heat
c. The cost of insulating a high temperature system is the exact same as a low temperature system
d. All of the above
Explanation: Thermodynamically, mechanical cooling (refrigeration) is much more energy-intensive and expensive to operate per BTU than direct heating methods. Therefore, preventing heat gain into a cooled space is economically more critical than preventing heat loss from a heated space. Source: Principles of HVAC and Refrigeration.
95. Moisture present in low temperature insulation material will cause ______________
a. Reduction in the insulating value of the material
b. Improvement in the insulating value of the materials
c. Decrease in the overall density of the material
d. All of the above
Explanation: Liquid water has a thermal conductivity over 20 times higher than trapped air. When moisture infiltrates porous insulation, it displaces the air pockets, drastically reducing the material's thermal resistance (R-value). Source: ASHRAE Fundamentals - Moisture Transport.
96. A process of heating and adjusting moisture in copra to facilitate the removal of oil during mechanical pressing.
a. Drying
b. Steaming
c. Conditioning
d. None of the above
Explanation: Conditioning is the explicit processing step of heating and strictly regulating the moisture content of copra (or other oilseeds) before pressing. This ruptures oil-bearing cells and reduces oil viscosity, maximizing extraction yields. Source: Agricultural Process Engineering / PAES.
97. One thousand fresh coconuts at roughly 800 grams per nut will produce approximately ___________ kg of copra.
a. 220 kg
b. 320 kg
c. 420 kg
d. None of the above
Explanation: Based on standard agricultural processing ratios, the meat of the coconut makes up roughly 30% of the nut's whole weight, and subsequent drying reduces that mass further. A yield of ~220 kg of dried copra from 1000 nuts is the standard industry estimate. Source: Philippine Agricultural Engineering Standards (PAES) - Copra Production.
98. It is an extruded foam highly utilized for low temperature systems such as refrigeration, cold-storage building, and sub-zero insulation.
a. Polystyrene foam (XPS)
b. PVC foam
c. Generic plastic foam
d. All of the above
Explanation: Extruded Polystyrene (XPS) foam features a closed-cell structure making it highly resistant to moisture absorption and vapor drive, establishing it as an industry standard for sub-zero and refrigeration structural insulation. Source: Refrigeration Systems and Insulation Standards.
99. It is essentially a specialized ceramic material explicitly designed to resist extremely high temperatures in the range of 1000 to 1800 C.
a. Refractory
b. Asbestos
c. Fiber glass
d. None of the above
Explanation: Refractories are robust, heat-resistant ceramic materials constructed to withstand extreme operating temperatures without melting or losing structural integrity. They line furnaces, kilns, and incinerators. Source: Materials Science and Engineering.
100. Essential factors that need to be carefully considered when selecting industrial insulators ______________
a. Expected operating temperature limits
b. Long term maintenance cost
c. Ability to resist mechanical wear and heat damage
d. All of the above
Explanation: Correct insulation specification requires assessing the full thermal operating profile, the required mechanical durability in the field, moisture resistance, and overall life-cycle economics including maintenance. Source: ASHRAE Insulation Guidelines.
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