Question

a) Describe radiation and conduction as modes of heat transfer; what are the key differences between them? [41 b) You are thinking of installing an observation window to a walk in fridge wall. Compare the rate of heat transfer of the original fridge wall (no window) with the new one (with window). The original wall has an area of 8m2 and is composed of three layers in series, 0.3 cm steel, 3 cm cork for insulation and a 2.5 cm fiberglass coating. The glass window to be installed has an area of 1 m2 and is 1.5 cm thick (leaving the remaining wall with an area of 7m2) [121 c) Assuming that the fridge with the window looses heat at faster rate, suggest three ways to slow the rate of heat loss. 141 d) Describe how boundary layers develop in laminar flow in a pipe from the entry point, use a diagram to support your answer. At which point will heat transfer rate be greatest? Data Steel k- 50 W/m K Cork k 0.043 W/m K Fiberglass k 0.048 W/m K Glass k-1.03 W/m K Internal Temperature T 5°C External Temperature T = 30°C

Answer 1

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Rey 30-5-こ 164-149 o. 0 1313 Less Heat Lass Los另with. Window

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the heat transfer rate in a boundary layer should be highest at the vertex of boundary layer i.e. at origin in above figure.