The walls of a refrigeration plant are composed of an insulating material (k=0.256 Kj per hour –m-C) 15 cm thick held between two layers of hollow blocks (k=4.2KJ/hr – m-C) each 15cm thick. The film coefficients are 90KJ/hr-m-C on the outside and 45 KJ/hr-m-C on the inside. Cold storage temperature is -10C and the ambient temperature is 30C. Determine the overall coefficient of heat transfer.

The walls of a refrigeration plant are composed of an insulating material (k=0.256 Kj per hour –m-C) 15 cm thick held between two layers of hollow blocks (k=4.2KJ/hr – m-C) each 15cm thick. The film coefficients are 90KJ/hr-m-C on the outside and 45 KJ/hr-m-C on the inside. Cold storage temperature is -10C and the ambient temperature is 30C. Determine the overall coefficient of heat transfer.