PH-2179 -- A Generalized Program for Steady-State System Simulation

The term "system simulation" when applied to such thermal systems as heating and cooling plants means the calculation or prediction of all crucial operating variables such as temperatures, pressures, and energy and fluid flow rates at a given time. The performance characteristics of all components including controls must be known, as well as input conditions to the system such as the temperatures and flow rates of water and air entering the system. A one-sentence definition of system simulation applicable to our purpose is that of predicting the operating quantities within a system (pressures, temperatures, energy- and fluid-flow rates) at the condition where all energy and material balances all equations ofstate of working substances, and all performance characteristics ofindividual components and controls are satisfied.

This paper presents a method for simulating thermal systems and a computer program based on that method. It is a generalized program in the sense that the same basic program applies to any system, so long as the performance equations of the components in the system are supplied as a subroutine. The program presented in this paper is not purported to be the final answer to steady-state system simulation of thermal systems. On the contrary this paper has been prepared through the stimulation of the ASHRAE Task Group on Energy Requirements for Heating and Cooling of Buildings in order to encourage experimentation in generalized system simulation with the intent of learning the pitfalls and suggesting improvements.