Heat Transfer - Video Lectures
Topic outline
-
-
Nusselt Number from Temperature Profile PageME-2014-S1-46-htThe non-dimensional fluid temperature profile near the surface of a convectively cooled flat plate is given by \[ \frac {T_w-T}{T_w-T_\infty } = a + b\frac {y}{L}+c\left (\frac {y}{L}\right )^2 \] where \(y\) is measured perpendicular to the plate, \(L\) is the plate length, and \(a\), \(b\) and \(c\) are arbitrary constants. \(T_w\) and \(T_\infty \) are wall and ambient temperatures, respectively. If the thermal conductivity of the fluid is \(k\) and the wall heat flux is \(q\), the Nusselt number \(\displaystyle \text {Nu} = \frac {q}{T_w-T_\infty }\frac {L}{k}\) is equal to
- \(a\)
- \(b\)
- \(2c\)
- \((b+2c)\)
-
Thermally Developed Flow for Constant Wall Heat Flux PageME-2019-S1-32The wall of a constant diameter pipe of length 1 m is heated uniformly with flux \(q\) by wrapping a heater coil around it. The flow at the inlet to the pipe is hydrodynamically fully developed. The fluid is incompressible and the flow is assumed to be laminar and steady all through the pipe. The bulk temperature of the fluid is equal to 0oC at the inlet and 50oC at the exit. The wall temperatures are measured at three locations, P, Q and R, as shown in the figure. The flow thermally develops after some distance from the inlet. The following measurements are made:
Point P Q R Wall Temperature (oC) 50 80 90
Among the locations P, Q and R, the flow is fully developed at
- P, Q and R
- P and Q only
- Q and R only
- R only
-
Temperature of Surface for Constant Heat Flux PageME-2022-S2-65Consider a hydrodynamically and thermally fully-developed, steady fluid flow of 1 kg/s in a uniformly heated pipe with diameter of 0.1 m and length of 40 m. A constant heat flux of magnitude 15000 W/m2 is imposed on the outer surface of the pipe. The bulk mean temperature of the fluid at the entrance to the pipe is 200oC. The Reynolds number (Re) of the flow is 85000, and the Prandtl number (Pr) of the fluid is 5. The thermal conductivity and the specific heat of the fluid are 0.08 W/(m.K) and 2600 J/(kg.K), respectively. The correlation \(\text{Nu} = 0.023\text{Re}^{0.8}\text{Pr}^{0.4}\) is applicable, where the Nusselt number (Nu) is defined on the basis of the pipe diameter. The pipe surface temperature at the exit is ______ oC (round off to the nearest integer).
-
Velocity and Heat Transfer Coefficient from Colburn Analogy Page2002-8-htAir flows through a smooth tube, 2.5 cm diameter and 10 m long, at 37\(^\circ \)C. If the pressure drop through the tube is 10000 Pa, estimate:
- the air velocity (in m/s) through the tube.
- the heat transfer coefficient (in W/m\(^2\).K) using Colburn Analogy [\(j_H = (\text {St})(\text {Pr})^{0.67}\)], where \(\text {St}\) is the Stanton Number and \(\text {Pr}\) is the Prandtl Number.
-
Heat Flux Estimation from Experiments Page2016-41-htIn an experimental setup, mineral oil is filled in between the narrow gap of two horizontal smooth plates. The setup has arrangements to maintain the plates at desired uniform temperatures. At these temperatures, ONLY the radiative heat flux is negligible. The thermal conductivity of the oil does not vary perceptibly in this temperature range. Consider four experiments at steady state under different experimental conditions, as shown in the figure below. The figure shows plate temperatures and the heat fluxes in the vertical direction.
What is the steady state heat flux (in W/m2) with the top plate at 70oC and the bottom plate at 40oC? _________ (26 / 39 / 42 / 63)
-
Heat Flux and Temperature for Convective Heat Transfer PageME-2013-50-51Water (specific heat, \(C_P=4.18\) kJ/[kg.K]) enters a pipe at a rate of 0.01 kg/s and a temperature of 20oC. The pipe, of diameter 50 mm and length 3 m, is subjected to a wall heat flux \(q_w\) in W/m2:
- If \(q_w=2500x\), where \(x\) is in m and in the direction of flow (\(x=0\) at the inlet), the bulk mean temperature of the water leaving the pipe in oC is _____ (42 / 62 / 74 / 104)
- If \(q_w=5000\) and the convection heat transfer coefficient at the pipe outlet is 1000 W/(m2.K), the temperature in oC at the inner surface of the pipe at the outlet is _____ (71 / 76 / 79 / 81)
-