Abstract
A good estimate of the cooling load is one vital aspect for achieving the optimal level of comfort and energy efficiency in buildings. Due to its relative simplicity, the Cooling Load Temperature Difference (CLTD) method is still used both in education and industry for cooling load calculations. However, one downside of using this method is the limited number of walls and roofs which do not represent effectively all commonly used wall and roof constructions. In this research, a transient heat transfer model was developed to find the (CLTD) values, for the most common external walls of buildings that have widespread use in Tripoli, Libya. The Finite difference method was used to solve the governing partial differential equations with appropriate initial and boundary conditions. A MATLAB program has been developed and used to solve the system of algebraic equations produced by applying the finite difference method to the governing differential equations. A comparison has been made between the computed results and ASHRAE CLTD values. At standard conditions specified in ASHRAE handbooks for the same wall with a default composition, a reasonably good agreement was found between computed and ASHRAE CLTD values for this wall. CLTD values have been generated for three different types of walls; Hollow concrete block, Limestone block, and Hollow brick. With these values, the cooling load calculation of buildings can be easily and manually performed with more accuracy. It is also concluded from the transient analysis that the limestone block walls provide the best thermal performance for unconditioned buildings whereas hollow brick walls are better for conditioned places.