SD-95-04-4 — Development of a Model to Simulate the Performance of Hydronic Radiant Cooling Ceilings

A significant amount of the electrical energy used to cool non-residential buildings equipped with all-air systems is drawn by the fans that transport the cool air through the thermal distribution system. Hydronic radiant cooling (RC) systems have the potential to reduce the amount of air transported through the building by separating the tasks of ventilation and thermal conditioning. Because of the physical properties of water, hydronic radiant cooling systems can transport a given amount of thermal energy using less than 5% of the otherwise necessary fan energy. This improvement alone significantly reduces the energy consumption and peak power requirement of the air conditioning system. Hydronic radiant cooling systems have been used for more than 30 years in hospital rooms to provide a draught-free, thermally stable environment. The energy savings and peak-load characteristics of these systems have not yet been analysed systematically. Moreover, adequate guidelines for design and control of these systems do not exist. This has prevented their widespread application to other building types. The evaluation of the theoretical performance of hydronic systems could be made most conveniently by computer models. Energy analysis programs such as DOE-2 do not have the capability to simulate hydronic radiant systems yet. The development of a model that can accurately simulate the dynamic performance of hydronic radiant cooling systems is described. The model can calculate loads, heat extraction rates, room air temperature, and room surface temperature distributions, and can be used to evaluate issues such as thermal comfort, controls, system sizing, system configuration, and dynamic response. The model was created with the Simulation Problem Analysis and Research Kernel (SPARK), developed at a national laboratory, which provides a methodology for describing and solving the dynamic, nonlinear equations that correspond to complex physical systems.

KEYWORDS: year 1995, calculating, performance, radiant cooling, ceiling cooling, water, energy conservation, energy consumption, air conditioning, peak load, computer programs, cooling load, air temperature, indoor, heat flow, temperature distribution, thermal comfort, controls, sizing, accuracy, comparing