4249 (RP-696) -- Evaluation of Service Hot Water Distribution System Losses in Residential and Commercial Installations: Part 1 - Field / Laboratory Experiments and Simulation Model PDF

Laboratory and field experiments were performed to provide data on heat losses from hot water piping systems. The objective of the research (ASHRAE Research Project 696) was to perform field experiments to determine heat loss in various piping systems. The piping systems, though, did not necessarily define the heat loss so as to be applicable to other systems of piping. Therefore, a numerical model was developed to simulate the heat loss, which is a more general and useful approach than field experiments. The laboratory and field experimental results were used, in part, as a comparison to the simulation results of a numerical model of heat loss (or gain) to water distribution piping systems. Experiments included the cases of noninsulated and insulated tubing over a range of flow rates and inlet water and ambient temperatures. Data obtained for both the residential and commercial installation field experiments consisted of water flow rates and water inlet and outlet temperatures. Analyses of the laboratory and field data are included in this paper along with an estimate of experimental error and uncertainty. The numerical model developed for estimating the heat loss (or heat gain) from insulated or noninsulated hot water pipes is discussed. The model calculates the two-dimensional temperature distribution in the water, pipe walls, and any insulation as a function of time and is capable of modeling steady flow or no flow (standby) conditions. The steady flow condition can be specified over a relatively short time span so that almost any draw schedule can be modeled. With the ability to model a range of parameters, the model can be used for comparative studies, such as establishing the heat loss differences between insulated and noninsulated piping, and for a companion paper.

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