Estimation of Hourly Solar Loads on the Surfaces of Moving Refrigerated Tractor Trailers Outfitted with Phase Change Materials (PCMs) for Several Routes across the Continental U.S.

Abstract

The primary objective of this thesis was to calculate solar loads, wind chill temperatures on the surfaces of moving refrigerated tractor trailers outfitted with phase change materials (PCMs) for several routes across the Continental United States. The second objective was to calculate hourly heat balances with more emphasis on the estimation of interior surface temperatures. PCMs have been widely tested and used in buildings during the past decades. As food transportation vehicles, experience different environmental conditions as they are in motion, the study of PCMs on food transportation vehicles could lead to new findings related to energy conservation. In this research work, a solar model was developed based on synthesized weather data files obtained from the National Solar Radiation Data Base (NSRDB), which contains weather information from 1961 through 1990 for 239 locations (TMY2 data) and weather information from 1991 through 2005 for 1020 locations (TMY3 data). The solar model was comprised of two parts, data extraction and solar load calculations. The data extraction part extracted the required fields from the TMY data and used them in the solar load calculations program to estimate the solar loads, wind chill temperatures and the interior surface temperatures of every exposed surface of a moving tractor trailer. These solar loads, wind chill temperatures and the interior surface temperatures would then be used in selecting the adequate type of PCMs for a particular route and time of year and to know, if the temperature where the PCMs will be placed will be "hot enough" to melt the PCMs and/or "cold enough" to solidify the PCMs. This is the case because PCMs are chosen, among other parameters, based on melting and solidification temperatures. In addition, the selection should also consider the construction of the truck, type of goods transported, indoor temperature of the truck's refrigerated compartment and the PCM placement on the walls. The results obtained by incorporating PCMs in standard trailer walls, showed that an average reduction in peak heat transfer rate of 29.1%, based on all surfaces (i.e., south, east, north, and west walls and the top surface), could be achieved. Overall average daily heat transfer reductions of 16.3% were observed in experiments of stationary standard trailer walls outfitted with PCMs. In conventional cargo trucks, the refrigeration unit is operated by burning fossil fuels, mainly diesel. Therefore, a decrease in refrigeration load, would have an impact in fuel consumption and in the reduction in size of the refrigeration equipment's.