EXPERIMENTAL AND NUMERICAL DETERMINATION OF A NEW WALL-HEAT-GAIN FUNCTION

A new 'wall-heat-gain function' is developed, which provides the heat entering a space through a wall under periodic outdoor conditions and constant indoor air temperature. The proposed function, which is much simpler than the well-known conduction transfer function, contains three coefficients U, w(1) and w(2) characterizing the wall and three parameters T-M, T-C and T-S characterizing the outdoor conditions (temperature and solar radiation). The wall coefficients U, w(1) and w(2) may be determined numerically by the use of the finite difference method or experimentally in the case of existing (built) walls of unknown properties. A related experimental set up has been developed. Ready to use values of the wall coefficients are provided for 15 typical wall constructions. The climatic parameters T-M, T-C and T-S either are available for some locations or may be easily calculated by least-squares fitting to local climatological data. In a modified form of the proposed function the three climatic parameters are reduced to two, which are available from ASHRAE for about 1000 stations around the world. The accuracy of the proposed wall heat gain function is very good for practical applications as proved by comparisons with corresponding finite difference solutions.