Heat Transfer interview questions

1. A.outer radius k/h for a cylinder below which adding insulation increases heat loss instead of reducing it
2. B.ratio of internal conduction resistance to surface convection resistance hL/k, with lumped-capacitance analysis valid below 0.1
3. C.conductive heat flux is proportional to the negative temperature gradient, with thermal conductivity as the constant
4. D.the ratio of thermal conductivity to the product of density and specific heat, governing how fast a temperature disturbance propagates

Answer + AI explanation with Pro

1. A.Fourier's law
2. B.Stefan-Boltzmann law
3. C.Biot number
4. D.Nusselt number

Answer + AI explanation with Pro

1. A.Fourier's law — the ratio of momentum diffusivity to thermal diffusivity, which fixes the relative thickness of the velocity and thermal boundary layers
2. B.Fourier's law — ratio of internal conduction resistance to surface convection resistance hL/k, with lumped-capacitance analysis valid below 0.1
3. C.Fourier's law — the ratio of thermal conductivity to the product of density and specific heat, governing how fast a temperature disturbance propagates
4. D.Fourier's law — conductive heat flux is proportional to the negative temperature gradient, with thermal conductivity as the constant

Answer + AI explanation with Pro

1. A.ratio of heat transfer with a fin to that from the bare base area, with fins justified only when it exceeds about 2
2. B.convective heat transfer rate equals hA times the temperature difference between the surface and the bulk fluid
3. C.sizing approach used when outlet temperatures are unknown, relating effectiveness to UA/Cmin and the capacity ratio
4. D.the ratio of thermal conductivity to the product of density and specific heat, governing how fast a temperature disturbance propagates

Answer + AI explanation with Pro

1. A.Fin effectiveness
2. B.Newton's law of cooling
3. C.Fourier's law
4. D.Thermal diffusivity

Answer + AI explanation with Pro

1. A.Newton's law of cooling — heat exchanger rating using UA times the log-mean temperature difference, with counter-flow giving a higher value than parallel flow for the same terminal temperatures
2. B.Newton's law of cooling — convective heat transfer rate equals hA times the temperature difference between the surface and the bulk fluid
3. C.Newton's law of cooling — the ratio of convective to conductive heat transfer across a boundary, so a value of one means pure conduction
4. D.Newton's law of cooling — conductive heat flux is proportional to the negative temperature gradient, with thermal conductivity as the constant

Answer + AI explanation with Pro

1. A.outer radius k/h for a cylinder below which adding insulation increases heat loss instead of reducing it
2. B.the ratio of thermal conductivity to the product of density and specific heat, governing how fast a temperature disturbance propagates
3. C.ratio of internal conduction resistance to surface convection resistance hL/k, with lumped-capacitance analysis valid below 0.1
4. D.a black body emits radiation at σT⁴ per unit area, with σ = 5.67 × 10⁻⁸ W/m²K⁴

Answer + AI explanation with Pro

1. A.LMTD method
2. B.Thermal diffusivity
3. C.Critical radius of insulation
4. D.Stefan-Boltzmann law

Answer + AI explanation with Pro

1. A.Stefan-Boltzmann law — a black body emits radiation at σT⁴ per unit area, with σ = 5.67 × 10⁻⁸ W/m²K⁴
2. B.Stefan-Boltzmann law — ratio of internal conduction resistance to surface convection resistance hL/k, with lumped-capacitance analysis valid below 0.1
3. C.Stefan-Boltzmann law — peak of the boiling curve beyond which a vapour film blankets the surface and wall temperature jumps, the burnout limit for boiler tubes
4. D.Stefan-Boltzmann law — outer radius k/h for a cylinder below which adding insulation increases heat loss instead of reducing it

Answer + AI explanation with Pro

1. A.ratio of internal conduction resistance to surface convection resistance hL/k, with lumped-capacitance analysis valid below 0.1
2. B.a black body emits radiation at σT⁴ per unit area, with σ = 5.67 × 10⁻⁸ W/m²K⁴
3. C.the fraction of radiation leaving one surface that is intercepted directly by another, depending only on geometry
4. D.the ratio of convective to conductive heat transfer across a boundary, so a value of one means pure conduction

Answer + AI explanation with Pro

1. A.Stefan-Boltzmann law
2. B.Fourier's law
3. C.Biot number
4. D.Newton's law of cooling

Answer + AI explanation with Pro

1. A.Biot number — peak of the boiling curve beyond which a vapour film blankets the surface and wall temperature jumps, the burnout limit for boiler tubes
2. B.Biot number — ratio of heat transfer with a fin to that from the bare base area, with fins justified only when it exceeds about 2
3. C.Biot number — the ratio of convective to conductive heat transfer across a boundary, so a value of one means pure conduction
4. D.Biot number — ratio of internal conduction resistance to surface convection resistance hL/k, with lumped-capacitance analysis valid below 0.1

Answer + AI explanation with Pro

1. A.convective heat transfer rate equals hA times the temperature difference between the surface and the bulk fluid
2. B.the ratio of momentum diffusivity to thermal diffusivity, which fixes the relative thickness of the velocity and thermal boundary layers
3. C.ratio of heat transfer with a fin to that from the bare base area, with fins justified only when it exceeds about 2
4. D.outer radius k/h for a cylinder below which adding insulation increases heat loss instead of reducing it

Answer + AI explanation with Pro

1. A.Radiation shape factor
2. B.Thermal diffusivity
3. C.Critical radius of insulation
4. D.Fin effectiveness

Answer + AI explanation with Pro

1. A.Critical radius of insulation — heat exchanger rating using UA times the log-mean temperature difference, with counter-flow giving a higher value than parallel flow for the same terminal temperatures
2. B.Critical radius of insulation — outer radius k/h for a cylinder below which adding insulation increases heat loss instead of reducing it
3. C.Critical radius of insulation — the ratio of momentum diffusivity to thermal diffusivity, which fixes the relative thickness of the velocity and thermal boundary layers
4. D.Critical radius of insulation — a black body emits radiation at σT⁴ per unit area, with σ = 5.67 × 10⁻⁸ W/m²K⁴

Answer + AI explanation with Pro

1. A.a black body emits radiation at σT⁴ per unit area, with σ = 5.67 × 10⁻⁸ W/m²K⁴
2. B.ratio of heat transfer with a fin to that from the bare base area, with fins justified only when it exceeds about 2
3. C.heat exchanger rating using UA times the log-mean temperature difference, with counter-flow giving a higher value than parallel flow for the same terminal temperatures
4. D.conductive heat flux is proportional to the negative temperature gradient, with thermal conductivity as the constant

Answer + AI explanation with Pro

1. A.Radiation shape factor
2. B.Critical radius of insulation
3. C.Fourier's law
4. D.Fin effectiveness

Answer + AI explanation with Pro

1. A.Fin effectiveness — sizing approach used when outlet temperatures are unknown, relating effectiveness to UA/Cmin and the capacity ratio
2. B.Fin effectiveness — convective heat transfer rate equals hA times the temperature difference between the surface and the bulk fluid
3. C.Fin effectiveness — peak of the boiling curve beyond which a vapour film blankets the surface and wall temperature jumps, the burnout limit for boiler tubes
4. D.Fin effectiveness — ratio of heat transfer with a fin to that from the bare base area, with fins justified only when it exceeds about 2

Answer + AI explanation with Pro

1. A.ratio of heat transfer with a fin to that from the bare base area, with fins justified only when it exceeds about 2
2. B.heat exchanger rating using UA times the log-mean temperature difference, with counter-flow giving a higher value than parallel flow for the same terminal temperatures
3. C.the ratio of momentum diffusivity to thermal diffusivity, which fixes the relative thickness of the velocity and thermal boundary layers
4. D.sizing approach used when outlet temperatures are unknown, relating effectiveness to UA/Cmin and the capacity ratio

Answer + AI explanation with Pro

1. A.Effectiveness-NTU method
2. B.Fourier's law
3. C.Biot number
4. D.LMTD method

Answer + AI explanation with Pro

1. A.LMTD method — heat exchanger rating using UA times the log-mean temperature difference, with counter-flow giving a higher value than parallel flow for the same terminal temperatures
2. B.LMTD method — ratio of heat transfer with a fin to that from the bare base area, with fins justified only when it exceeds about 2
3. C.LMTD method — sizing approach used when outlet temperatures are unknown, relating effectiveness to UA/Cmin and the capacity ratio
4. D.LMTD method — a black body emits radiation at σT⁴ per unit area, with σ = 5.67 × 10⁻⁸ W/m²K⁴

Answer + AI explanation with Pro

1. A.heat exchanger rating using UA times the log-mean temperature difference, with counter-flow giving a higher value than parallel flow for the same terminal temperatures
2. B.peak of the boiling curve beyond which a vapour film blankets the surface and wall temperature jumps, the burnout limit for boiler tubes
3. C.sizing approach used when outlet temperatures are unknown, relating effectiveness to UA/Cmin and the capacity ratio
4. D.the ratio of momentum diffusivity to thermal diffusivity, which fixes the relative thickness of the velocity and thermal boundary layers

Answer + AI explanation with Pro

1. A.Critical radius of insulation
2. B.Nusselt number
3. C.Effectiveness-NTU method
4. D.Radiation shape factor

Answer + AI explanation with Pro

1. A.Effectiveness-NTU method — peak of the boiling curve beyond which a vapour film blankets the surface and wall temperature jumps, the burnout limit for boiler tubes
2. B.Effectiveness-NTU method — ratio of heat transfer with a fin to that from the bare base area, with fins justified only when it exceeds about 2
3. C.Effectiveness-NTU method — the ratio of convective to conductive heat transfer across a boundary, so a value of one means pure conduction
4. D.Effectiveness-NTU method — sizing approach used when outlet temperatures are unknown, relating effectiveness to UA/Cmin and the capacity ratio

Answer + AI explanation with Pro

1. A.a black body emits radiation at σT⁴ per unit area, with σ = 5.67 × 10⁻⁸ W/m²K⁴
2. B.outer radius k/h for a cylinder below which adding insulation increases heat loss instead of reducing it
3. C.the ratio of thermal conductivity to the product of density and specific heat, governing how fast a temperature disturbance propagates
4. D.peak of the boiling curve beyond which a vapour film blankets the surface and wall temperature jumps, the burnout limit for boiler tubes

Answer + AI explanation with Pro

1. A.Fourier's law
2. B.Critical heat flux
3. C.Radiation shape factor
4. D.Stefan-Boltzmann law

Answer + AI explanation with Pro

1. A.Critical heat flux — convective heat transfer rate equals hA times the temperature difference between the surface and the bulk fluid
2. B.Critical heat flux — peak of the boiling curve beyond which a vapour film blankets the surface and wall temperature jumps, the burnout limit for boiler tubes
3. C.Critical heat flux — ratio of internal conduction resistance to surface convection resistance hL/k, with lumped-capacitance analysis valid below 0.1
4. D.Critical heat flux — conductive heat flux is proportional to the negative temperature gradient, with thermal conductivity as the constant

Answer + AI explanation with Pro

1. A.heat exchanger rating using UA times the log-mean temperature difference, with counter-flow giving a higher value than parallel flow for the same terminal temperatures
2. B.ratio of heat transfer with a fin to that from the bare base area, with fins justified only when it exceeds about 2
3. C.conductive heat flux is proportional to the negative temperature gradient, with thermal conductivity as the constant
4. D.the ratio of convective to conductive heat transfer across a boundary, so a value of one means pure conduction

Answer + AI explanation with Pro

1. A.Biot number
2. B.Nusselt number
3. C.Radiation shape factor
4. D.Effectiveness-NTU method

Answer + AI explanation with Pro

1. A.Nusselt number — the ratio of convective to conductive heat transfer across a boundary, so a value of one means pure conduction
2. B.Nusselt number — sizing approach used when outlet temperatures are unknown, relating effectiveness to UA/Cmin and the capacity ratio
3. C.Nusselt number — convective heat transfer rate equals hA times the temperature difference between the surface and the bulk fluid
4. D.Nusselt number — conductive heat flux is proportional to the negative temperature gradient, with thermal conductivity as the constant

Answer + AI explanation with Pro