Analysis of air-to-air heat exchanger performance data taken under the Residential Standards Demonstration Program [report]

M.K. Drost
1990 unpublished
The Bonneville Power Administration (BPA) initiated the Residential Standards Demonstration Program (RSDP) in 1983 to determine the costs and thermal performance improvements associated with increased levels of thermal integrity in new residences, as proposed by the Northwest Power Planning Council in their Model Conservation Standards (MCS). The program resulted in the construction of approximately 430 new residences, built to thermal performance standards, as dictated by the MCS in each of
more » ... e MCS in each of three climate zones in the region. A subset of the residences has been included in the End-Use Load and Consumer Assessment Program (ELCAP) being conducted by the Pacific Northwest Laboratory (PNL) for the Bonneville Power Administration (BPA). These structures are metered to record hourly energy consumption for several end-uses. Many of the structures built to the MCS include air-to-air heat exchangers (AAHXs) to provide ventilation for maintenance of indoor air quality and comfort. Of the 71 MCS structures included in the ELCAP sample, 38 included air-to-air heat exchangers and had sufficient data to allow an analysis of both use patterns and thermal performance. This report describes the results of the analysis of the AAHX installations using the data collected as part of ELCAP. The research had two objectives: to investigate AAHX use patterns and to determine the thermal performance of AAHX installations. The method used for analyzing use patterns consisted of determining the utilization of the AAHX, where utilization is defined as the ratio of actual AAHX energy consumption per time period divided by maximum AAHX energy consumption. Annual utilization was investigated by plotting daily average utilization as a time series. Daily utilization was investigated by determining the hourly utilization for a typical day. Thermal performance was determined by selecting time periods with high utilization (implying nearly continuous AAHX operation). For these time periods, several thermal performance characteristics were first law efficiency, temperature of the intake air (TIA) living space and displaced space heating energy (Qsav). i i i determined, including as it enters the The calculation of the last two performance characteristics depended on knowing air flow rates through the AAHX. The ELCAP measurement protocols did not include measurement of air flow rates. Therefore, the best available information was one-time measurements of air flow made for each residence. To the extent that these values do not represent actual air flow for the time series data, errors wil l be introduced to the calculation of TIA and Osav· The results of the utilization analysis showed that there is substantial variation in AAHX utilization. The evaluation of AAHX annual utilization showed a range from almost continuous use to no use at all. Several archetypical patterns of annual utilization were identified. The average mean utilization for all 38 sites implied that the typical AAHX device would be operated approximately 7 hours per day, however, the standard deviation around the mean approximately equaled the mean value. This implied that a large variation in mean annual utilization did not appear to be influenced by either seasonal temperature variations or climate zones. Typical daily utilization values did not exhibit any dominant use patterns. The investigation of thermal performance showed that latent heat effects (condensation of water vapor in the exhaust air stream) did not have a significant impact on thermal performance. The mean annual first law efficiency for the 25 available sites was determined to be 52%, but there was a substantial standard deviation around the mean. Of the 25 sites, 11 had sufficient data to calculate the mean annual displaced space heating energy . This was 743 kWh/yr with a mean annual AAHX energy consumption of 220 kWh/yr. Again, there was a large standard deviation around the mean values, suggesting a large variation in the mean values for the 11 sites. In general, the investigations reported in this document show that mean annual AAHX utilization varies significantly between installations as do the daily use patterns. The thermal performance analysis tends to confirm results of previous investigators with the exception that this investigation seemed to show that latent heat effects are relatively important. iv CONTENTS
doi:10.2172/7157496 fatcat:ywksewlsozfuhlfk7zk4mzrtja