Answer Happy

Q4 A refrigerated store room stands in a warehouse where the air temperature is 20°C. The surface temperature on the outside of the refrigerated store is 16°C. The side walls of the store are made up of one layer 30 mm thick and have an equivalent thermal conductivity of 0.1 W/m K. The heat transfer coefficient between the outside wall and room air is 10 W/m2K. Assume one dimensional conduction through the one layer side walls. (a) Draw a diagram to show the parameters associated with each of the thermal resistance layers. (4 marks] [6 marks] (b) Calculate the net heat flow per unit area. (c) Calculate the surface temperature on the inside surface of the store wall. [6 marks] (d) Having seen the performance of the single layer wall, a decision is made to upgrade the wall for this refrigeration store to a composite wall with the construction details shown below, what would be the new overall thermal transmittance. [14 marks]