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1) Which surface can be best described as a radiation shield? a. the surface which has very high absorptivity b. the surface which has very high transmissivity c. the surface which has very high reflectivity d. none of the above
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2) Which object can be used as a radiation shield? a. polished transparent glass b. mirror c. rubber d. all of the above
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3) Gases absorb and emit radiant energy a. in all wavelengths over the entire spectrum (λ = 0 to ∞) b. only between narrow ranges of wavelengths c. only at single constant wavelength d. unpredictable
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4) Which among the following factors is/are taken into account in calculation of radiation emitted or absorbed by a gas layer? a. thickness of the gas layer b. shape of the gas enclosure c. pressure in gas enclosure d. all of the above
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5) How is the incident radiation absorbed by a gas layer? a. A gas layer absorbs incident radiation slowly b. A gas layer absorbs incident radiation rapidly c. doesn't matter d. unpredictable
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6) What are the compact heat exchangers? a. the heat exchangers having small surface area per unit volume b. the heat exchangers having large surface area per unit volume c. the heat exchangers having small surface area per unit weight d. the heat exchangers having large surface area per unit weight
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7) Which of the following can be considered as more compact efficient heat exchanger? a. Car radiators b. Stirling engine regenerator c. Ceramic regenerator in gas turbine d. none of the above
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8) The compact heat exchangers are commonly used in a. gas to gas heat transfer b. gas to liquid heat transfer c. both a. and b. d. none of the above
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9) Usually, the flow arrangement of two fluids in compact heat exchangers is a. parallel flow b. counter flow c. cross flow d. none of the above
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10) What is effectiveness of fin? a. the ratio of actual heat transferred from fin area to the heat which would be transferred if entire fin area was at base temperature b. the heat which would be transferred if entire fin area was at base temperature to the ratio of actual heat transferred from fin area c. the heat which would be transferred if entire fin area was at minimum temperature to the ratio of actual heat transferred from fin area d. the ratio of actual heat transferred from fin area to the heat which would be transferred if entire fin area was at minimum temperature
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11) What is the effect of thermal conductivity k on fin effectiveness? a. fin is effective for smaller value of thermal conductivity k b. fin is effective for larger value of thermal conductivity k c. thermal conductivity k does not affect the fin effectiveness d. cannot say
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12) What is the effect of convective heat transfer coefficient h on fin effectiveness? a. fin is effective if the value of convective heat transfer coefficient h is small b. fin is effective if the value of convective heat transfer coefficient h is large c. fin effectiveness does not affected by the value of convective heat transfer coefficient h d. none of the above
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13) Which medium of surrounding is better for fin effectiveness? a. gas medium b. liquid medium c. fins have same effectiveness in both the gas and liquid mediums d. none of the above
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14) For effective working of fins, the thickness of the fines should be a. large b. small c. thickness of fin does not affect the fin effectiveness d. unpredictable
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15) Aluminum is used as a fin material because a. it has higher convection heat transfer coefficient b. it has higher thermal conductivity c. it has lower convection heat transfer coefficient d. it has lower thermal conductivity
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16) Which of the following arrangements of fins is more effective for the same base area? 1. Large number of closely spaced fins 2. Small number of thick fins a. Arrangement 1 b. Arrangement 2 c. both the arrangements 1 and 2 are similarly effective d. unpredictable
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17) Consider an element with finite dimensions. In general which among the following equations is correct for change in energy of element during a time span dt? a. [Heat generated in the element during time dt] + [Heat flow into the element during time dt] + [Heat flow out of the element during time dt] b. [Heat generated in the element during time dt] + [Heat flow into the element during time dt] – [Heat flow out of the element during time dt] c. [Heat generated in the element during time dt] – [Heat flow into the element during time dt] – [Heat flow out of the element during time dt] d. none of the above
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18) When does the general heat conduction equation which gives the temperature distribution and conduction heat flow in an isotropic solid reduce to Laplace equation? a. if the body or element is in unsteady-state with heat generation b. if the body or element is in steady-state with heat generation c. if the body or element is in unsteady-state with no heat generation d. if the body or element is in steady-state with no heat generation
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19) Generally the external thermal resistance between the surface of the body and the environment is a. less than the internal conduction resistance in the body b. more than the internal conduction resistance in the body c. same as the internal conduction resistance in the body d. none of the above
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20) Suppose that a hot metal ball is immersed in cold water, then temperature distribution in the body depends upon a. thermal conductivity of the body b. convective heat transfer from the body surface to water c. both a. and b. d. none of the above
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