posted 10 months ago

\text { Kinematic Viscosity }=7.65 \times 10^{-5} \mathrm{~m}^{2} / \mathrm{s}

\text { Thermal conductivity }=0.0549 \mathrm{~W} /(\mathrm{m}-\mathrm{K})

\text { Prandtl number }=0.72

posted 10 months ago

For fins of equal length, which fin has the largest heat transfer rate? Assume the gas properties are those of air atT=350K. Use correlations in Table 7.3 from the book.

posted 10 months ago

a) At 2.5m/s air flow, what is the rate of heat transfer from the first strip? The fifth strip? The tenthstrip? All the strips (average)?

b) For air velocities of 2, 5, and 10 m/s, determine the heat transfer for all the locations of part (a).Represent your results in tabular or bar graph.

c) Repeat part (b), but under conditions for which the flow is fully turbulent over the entire array strips.

posted 10 months ago

posted 10 months ago

Inner diameter of pipe12mm

Outer diameter of pipe14mmLonath of pino

Length of pipe = 1m%

Blue cavity is a 30mm by 30mm box with length 1m

posted 10 months ago

(a) Is the heat exchanger operating in a parallel flow or in a counter flow configuration? Sketch the temperatures through the heat exchanger using a diagram similar to Figure 11.7 or 11.8.

(b) What is the heat exchanger effectiveness, ɛ? What is the NTU? Phase change does not occur in either fluid. Partial Ans: NTU=2.75 (may need to use Fig. 11.10 or 11.11 as appropriate).

(c) If the hot fluid is ammonia gas at a flowrate of 0.2 kg/s, what is the overall heat transfer in the heat exchanger? Ans: 42.4 kW

posted 10 months ago

(a) If the plate is held such that its longest dimension (length) is vertical, what is the average convective heat transfer coefficient over the plate immediately after it is moved to the cooling area? Ans: 7.45 W/m?-K

(b) Assuming that the convective heat transfer coefficient does not change significantly over time, how long might it take for the plate to cool to 45°C? Ans: 53 min

(c) If the surfaces around the plate in the cooling area are large and at a constant temperature of 27°C,would radiation heat transfer be potentially significant in this problem? Assume that the copper emissivity is equivalent to a stably oxidized surface at 600K (see Table A.11), and evaluate the radiation heat flux at the start of the cooling. Compare to the convection heat flux at the start of cooling.

posted 10 months ago

(b) If air blows around the pipe (perpendicular to the pipe axis) with a velocity of 10 m/s and a freestream temperature of 27°C, what is the outlet temperature of the water? (Hint: review the last part of Ch. 8.3.3;you can neglect the conduction resistance of the pipe wall and assume that because it is so thin, the inner diameter and outer diameter are essentially the same). Is this result surprising to you? Why do you think it is so different from part (a)? Partial Ans: 94.3°C

(a) What is the outlet temperature of the water in the tube if the tube surface temperature can be maintained constant at 27°C? Ans: 33.7°C

posted 10 months ago

posted 10 months ago