27 real Heat Transfer questions from the Chemical Core bank, as asked in Indian campus drives and tech interviews. Every question has a verified answer and an AI-tutor explanation on placd — free to start.
1. What is Fourier's law?
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A.plot of heat flux against wall superheat through nucleate, transition and film regimes; the peak is the critical heat flux beyond which tube burnout occurs
B.conduction rate is proportional to area and to the negative temperature gradient, with thermal conductivity as the proportionality constant
C.black-body emissive power is proportional to the fourth power of absolute temperature with constant 5.67 × 10⁻⁸ W/m²K⁴
D.outer radius (k/h for a cylinder) below which adding insulation to a small pipe increases heat loss because the outer area grows faster than resistance
2. Which term means: "conduction rate is proportional to area and to the negative temperature gradient, with thermal conductivity as the proportionality constant"?
A.Fourier's law — plot of heat flux against wall superheat through nucleate, transition and film regimes; the peak is the critical heat flux beyond which tube burnout occurs
B.Fourier's law — outer radius (k/h for a cylinder) below which adding insulation to a small pipe increases heat loss because the outer area grows faster than resistance
C.Fourier's law — logarithmic mean of the two terminal temperature differences, the correct mean driving force for pure counter-current or co-current exchangers
D.Fourier's law — conduction rate is proportional to area and to the negative temperature gradient, with thermal conductivity as the proportionality constant
A.reciprocal of the sum of inside film, wall, outside film and fouling resistances in series, used in Q = U·A·ΔT
B.plot of heat flux against wall superheat through nucleate, transition and film regimes; the peak is the critical heat flux beyond which tube burnout occurs
C.convective heat flux equals the film heat transfer coefficient times the temperature difference between surface and bulk fluid
D.black-body emissive power is proportional to the fourth power of absolute temperature with constant 5.67 × 10⁻⁸ W/m²K⁴
A.Newton's law of cooling — plot of heat flux against wall superheat through nucleate, transition and film regimes; the peak is the critical heat flux beyond which tube burnout occurs
B.Newton's law of cooling — reciprocal of the sum of inside film, wall, outside film and fouling resistances in series, used in Q = U·A·ΔT
C.Newton's law of cooling — conduction rate is proportional to area and to the negative temperature gradient, with thermal conductivity as the proportionality constant
D.Newton's law of cooling — convective heat flux equals the film heat transfer coefficient times the temperature difference between surface and bulk fluid
A.Stefan-Boltzmann law — reciprocal of the sum of inside film, wall, outside film and fouling resistances in series, used in Q = U·A·ΔT
B.Stefan-Boltzmann law — black-body emissive power is proportional to the fourth power of absolute temperature with constant 5.67 × 10⁻⁸ W/m²K⁴
C.Stefan-Boltzmann law — outer radius (k/h for a cylinder) below which adding insulation to a small pipe increases heat loss because the outer area grows faster than resistance
D.Stefan-Boltzmann law — convective heat flux equals the film heat transfer coefficient times the temperature difference between surface and bulk fluid
A.outer radius (k/h for a cylinder) below which adding insulation to a small pipe increases heat loss because the outer area grows faster than resistance
B.plot of heat flux against wall superheat through nucleate, transition and film regimes; the peak is the critical heat flux beyond which tube burnout occurs
C.dimensionless ratio of convective to conductive heat transfer, hD/k, which convection correlations are written to predict
D.logarithmic mean of the two terminal temperature differences, the correct mean driving force for pure counter-current or co-current exchangers
A.Nusselt number — convective heat flux equals the film heat transfer coefficient times the temperature difference between surface and bulk fluid
B.Nusselt number — black-body emissive power is proportional to the fourth power of absolute temperature with constant 5.67 × 10⁻⁸ W/m²K⁴
C.Nusselt number — dimensionless ratio of convective to conductive heat transfer, hD/k, which convection correlations are written to predict
D.Nusselt number — logarithmic mean of the two terminal temperature differences, the correct mean driving force for pure counter-current or co-current exchangers
A.Dittus-Boelter correlation — conduction rate is proportional to area and to the negative temperature gradient, with thermal conductivity as the proportionality constant
B.Dittus-Boelter correlation — turbulent pipe-flow relation Nu = 0.023 Re^0.8 Pr^n with n = 0.4 for heating and 0.3 for cooling of the fluid
C.Dittus-Boelter correlation — convective heat flux equals the film heat transfer coefficient times the temperature difference between surface and bulk fluid
D.Dittus-Boelter correlation — dimensionless ratio of convective to conductive heat transfer, hD/k, which convection correlations are written to predict
A.Overall heat transfer coefficient — dimensionless ratio of convective to conductive heat transfer, hD/k, which convection correlations are written to predict
B.Overall heat transfer coefficient — reciprocal of the sum of inside film, wall, outside film and fouling resistances in series, used in Q = U·A·ΔT
C.Overall heat transfer coefficient — convective heat flux equals the film heat transfer coefficient times the temperature difference between surface and bulk fluid
D.Overall heat transfer coefficient — logarithmic mean of the two terminal temperature differences, the correct mean driving force for pure counter-current or co-current exchangers
A.black-body emissive power is proportional to the fourth power of absolute temperature with constant 5.67 × 10⁻⁸ W/m²K⁴
B.plot of heat flux against wall superheat through nucleate, transition and film regimes; the peak is the critical heat flux beyond which tube burnout occurs
C.logarithmic mean of the two terminal temperature differences, the correct mean driving force for pure counter-current or co-current exchangers
D.dimensionless ratio of convective to conductive heat transfer, hD/k, which convection correlations are written to predict
20. Which term means: "logarithmic mean of the two terminal temperature differences, the correct mean driving force for pure counter-current or co-current exchangers"?
A.LMTD — logarithmic mean of the two terminal temperature differences, the correct mean driving force for pure counter-current or co-current exchangers
B.LMTD — convective heat flux equals the film heat transfer coefficient times the temperature difference between surface and bulk fluid
C.LMTD — black-body emissive power is proportional to the fourth power of absolute temperature with constant 5.67 × 10⁻⁸ W/m²K⁴
D.LMTD — turbulent pipe-flow relation Nu = 0.023 Re^0.8 Pr^n with n = 0.4 for heating and 0.3 for cooling of the fluid
A.turbulent pipe-flow relation Nu = 0.023 Re^0.8 Pr^n with n = 0.4 for heating and 0.3 for cooling of the fluid
B.convective heat flux equals the film heat transfer coefficient times the temperature difference between surface and bulk fluid
C.outer radius (k/h for a cylinder) below which adding insulation to a small pipe increases heat loss because the outer area grows faster than resistance
D.black-body emissive power is proportional to the fourth power of absolute temperature with constant 5.67 × 10⁻⁸ W/m²K⁴
23. Which term means: "outer radius (k/h for a cylinder) below which adding insulation to a small pipe increases heat loss because the outer area grows faster than resistance"?
A.Critical radius of insulation — logarithmic mean of the two terminal temperature differences, the correct mean driving force for pure counter-current or co-current exchangers
B.Critical radius of insulation — outer radius (k/h for a cylinder) below which adding insulation to a small pipe increases heat loss because the outer area grows faster than resistance
C.Critical radius of insulation — reciprocal of the sum of inside film, wall, outside film and fouling resistances in series, used in Q = U·A·ΔT
D.Critical radius of insulation — plot of heat flux against wall superheat through nucleate, transition and film regimes; the peak is the critical heat flux beyond which tube burnout occurs
A.plot of heat flux against wall superheat through nucleate, transition and film regimes; the peak is the critical heat flux beyond which tube burnout occurs
B.turbulent pipe-flow relation Nu = 0.023 Re^0.8 Pr^n with n = 0.4 for heating and 0.3 for cooling of the fluid
C.reciprocal of the sum of inside film, wall, outside film and fouling resistances in series, used in Q = U·A·ΔT
D.conduction rate is proportional to area and to the negative temperature gradient, with thermal conductivity as the proportionality constant
26. Which term means: "plot of heat flux against wall superheat through nucleate, transition and film regimes; the peak is the critical heat flux beyond which tube burnout occurs"?
A.Boiling curve — dimensionless ratio of convective to conductive heat transfer, hD/k, which convection correlations are written to predict
B.Boiling curve — turbulent pipe-flow relation Nu = 0.023 Re^0.8 Pr^n with n = 0.4 for heating and 0.3 for cooling of the fluid
C.Boiling curve — black-body emissive power is proportional to the fourth power of absolute temperature with constant 5.67 × 10⁻⁸ W/m²K⁴
D.Boiling curve — plot of heat flux against wall superheat through nucleate, transition and film regimes; the peak is the critical heat flux beyond which tube burnout occurs
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