A domestic pitched roof of tiles on felt sacking with a plasterboard ceiling has an existing u-value of 1.9w/m2k. Calculate the minimum thickness of fibre glass insulation in the roof space required to give the roof a new u-value of 0.25w/m2k. The thermal conductivity of the fibre glass used is 0.04w/mk

There is a 1.20-cm-thick stagnant air pocket. A) What thickness of cork would have the same R-factor as the stagnant air pocket? The thermal conductivity of air is 0.0230 W/m·K and of cork is 0.0460 W/m·K.in cm  B) What thickness of tin would be required for the same R-factor as a 1.20-cm-thick stagnant air pocket? The thermal conductivity of air is 0.0230 W/m·K and of tin is 66.8 W/m·K . in m i asked how to do this but got the wrong soloution

You are designing a 3m x 3m floor with radiant heating.  The floor has 12 parallel pex pipes (k = 40 W/mK) of L = 3m, OD = 25mm and ID = 20mm.  Hot water (TInfintiy 1 = 90oC, h = 200 W/m2K) runs through the pipes continuously.  The surface below the pipes is perfectly insulated.  Above the pipes, there is a 3mm layer of bonding material (? = 12 W/mK) and a 9mm layer of tile (k = 2 W/mK).  Above the tile, there is air (TInfinity 2 = 25oC, h = 20 W/m2K). Properties of Air: k = 0.025 W/mK, Pr = 0.72, v = 1.847 x 10−5, u = 16.84 x 10−6, p = 1.2 kg/m3, B = 1/Tf (ideal gas),  Hint: Assume that the “layer” of pipe starts at the center point (e.g. for conduction purposes, the pipe is OD divided by 2 thick).  For convection, consider the entire pipe surface. a) What is the total heat rate entering the room above the floor? b) What is the temperature of the top of the tile?

A steel pipe with heat transfer coefficient of 42 W/mK contains flowing water. The outer diameter of the pipe is 90 mm and the wall thickness is 3mm. Calculate: i. The heat loss by convection and conduction per meter length of un-insulated pipe when the water temperature is 14°C, the outside air temperature is -10°C, the water side heat transfer coefficient is 30 KW/m^2K and the outside heat transfer coefficient is 20 KW/m^2K. ii. Calculate the corresponding heat loss when the pipe is lagged with insulation having an outer diameter of 200 mm, and thermal conductivity of K = 0.05 W/mK