| dc.description.abstract | Heat recovery ventilators, or HRVs, exhaust stale indoor air and supply fresh outdoor air while also transferring heat between the two airstreams via a heat exchange core. Considering the energy efficiency and energy savings of HRVs, a thesis project was inspired that focused on the thermal performance of these devices. In particular, this thesis project centered on: (1) designing, developing, and constructing a test setup for data collection on recovery ventilators based on Canadian Standards Association standard C439, (2) using the test setup to generate a data base of HRV test data for a wide range of outdoor air temperatures, and (3) investigating the effects of outdoor air temperature on the apparent effectiveness and sensible heat-recovery efficiency of an HRV with the intention of promoting applications and improving operations.
A major goal of this research is to investigate HRV performance as characterized by two important parameters, namely, the apparent effectiveness, ε, and sensible heat-recovery efficiency, ESHR. In support of this investigation, a total of 33 tests were conducted on the Fantech SHR200 HRV unit, and then this data file was used to determine the unit’s ε and ESHR for a range of representative hot outdoor air temperatures, namely, 88 °F to 112 °F, while maintaining a rated volumetric flowrate of approximately 195 CFM. During testing, these supply inlet airstream temperatures were achieved via an electric duct heater, which in turn enabled the HRV to perform in the cooling mode.
The results from the 33 tests showed proportional relationships for both ε and ESHR parameters versus outdoor air temperature. Apparent effectiveness, ε, increased slightly from 55% to 60% as the hot outdoor air temperature increased from about 88 °F to 112 °F. A plot of ε versus outdoor air temperature fit with a linear regression produced an R-squared value of 0.3155, indicating that the linear model partially fits the data. The sensible heat-recovery efficiency ESHR increased from 32% to 48% as the hot outdoor air temperature increased over the aforementioned min-to-max range, namely, about 88 °F to 112 °F. For ESHR versus outdoor air temperature, the R-squared value of the linear regression was 0.7540, indicating that most of the linear model fits the data. In comparison, the parameter ESHR versus outdoor air temperature is better fitted by a linear model compared to the parameter ε versus outdoor air temperature. Even so, the application of a linear trendline for both data sets was verified through a p-test and by plotting residuals versus fits and normal probability plots. Such verification was necessary to substantiate the statistical significance of both parameters, ε and ESHR, with outdoor air temperature.
Based on an analysis of the HRV, engineers can be assured that the apparent effectiveness, ε, and sensible heat-recovery efficiency, ESHR, of an HRV does not suffer or worsen as the hot outdoor air temperature increases, which is an important and even somewhat unexpected finding. On the contrary, the observed 5% increase in ε (55% to 60%) and the observed 16% increase in ESHR (32% to 48%) suggests that HRV performance adapts and even improves as hot outdoor air temperature rises. These performance results support adopting HRVs for use in improving indoor air quality while increasing one’s confidence that HRVs can lead to energy efficiency and savings even in hot outdoor air temperatures. | en |
