HEAT AND FLUID MECHANICS

HEAT TRANSFER AND FLUID MECHANICS

HEAT TRANSFER AND FLUID MECHANICS

Question 1.

A long copper tube is used in an apparatus for heat-transfer measurement. The tube has an internal diameter of 10 mm an external diameter of 20 mm and a thermocouple located in the wall. The thermocouple indicates the temperature of the copper at a radius of 8 mm from the centre line of the tube. On a particular occasion, the thermocouple indicates a temperature of 60 oC when the steady inward radial heat transfer rate per length of tube is 100 W/mm. Assume that the inner and outer surface temperatures of the tube are uniform and that the thermal conductivity of the copper is uniform and equal to 396 W/m K. Calculate the inner and outers surface temperatures of the tube.

Question 2.

A composite wall of a cold store has 150 mm of concrete on the outside, 60 mm of cork insulation inside the concrete, and a 20 mm layer of wood to protect the cork. The temperature of the outside surface of the composite wall is 20o C and that of the inside surface is -4o C. The thermal conductivities of the concrete, cork and wood are 0.92 W/m K, 0.036 W/m K and 0.12 W/m K. Estimate the heat-transfer rate per area through the composite wall and the temperatures at the interfaces, neglecting any interfacial resistance.

After calculations in the formula, we found the temperature to be 18.038=18 C.

The steady rate of heat transfer through window glass is then

The inner surface temperature of the window glass can be determined from

Question 3.



Question 4.

A spherical vessel of diameter 1 m contains liquid oxygen at a temperature of - 183o C. It has two layers of lagging each 0.10 m thick. The inner layer has a thermal conductivity of 0.050 W/m K and the outer 0.061 W/m K. The outer surface temperature is 15o C. Find the heat-transfer rate into the vessel. Neglect interfacial resistances.

Question 5.

Question 6.

Question 7.

Question 8.

Let T1=T

And T2=Ts

We can multiply the second equation by DoL to obtain the following result.

We know that the outside heat transfer coefficient is given by the equation A/(Tg - Tw)0.25, where A = 9.2 kW/m2/K0.75. = 9200 W(K0.75. We know that Tg = 110oC, but we do not know the average wall temperature Tw. We do know, however, that the transfer to the condensing fluid must be the same as the heat transfer from the ethylene glycol to the outer tube wall.

D=2r, so the 2 Pi factor comes in the numerator

Hence,

Hence, proved!

Question 9.



Then the ratio of the heat transfer becomes

Question 10.

Let, Ti= ?c

Regression (Regression) the nature of the problem in machine learning, training and forecasting. The regression divided into linear regression and nonlinear regression, which is built on the properties x and objectively. The assumption of a linear relationship (hypothesis). For each training sample, we must also be given to the output of the characteristic (feature) and category (class). Regression problems belong to the supervisory learning (supervised ...