Abstract

TANGWE, S.  and  KUSAKANA, K.. Using statistical tests to compare the coefficient of performance of air source heat pump water heaters. J. energy South. Afr. [online]. 2022, vol.33, n.1, pp.40-51. ISSN 2413-3051.  http://dx.doi.org/10.17159/2413-3051/2022/v33i1a7943.

The study compared the coefficient of performance (COP) of two residential types of air source heat pump (ASHP) water heaters using statistical tests. The COPs were determined from the controlled volume of hot water (150, 50 and 100 L) drawn off from each tank at different time of use (morning, afternoon and evening) periods during summer and winter. Power meters, flow meters, and temperature sensors were installed on both types of ASHP water heater to measure the data needed to determine the COPs. The results showed that the mean COPs of the split and integrated type ASHP water heaters were 2.965 and 2.652 for summer and 2.657 and 2.202 for winter. In addition, the p-values of the groups COPs for the split and integrated type ASHP water heaters during winter and summer were 7.09 x 10^-24 and 1.01 x 10¹¹, based on the one-way ANOVA and the Kruskal-Wallis tests. It can be concluded that, despite the year-round performance of both the split and integrated type ASHP water heaters, there is a significant difference in COP at 1% significance level among the four groups. Furthermore, both statistical tests confirmed these outcomes in the comparisons of the mean COPs among the four groups based on the multiple comparison algorithm.HIGHLIGHTS: • One-way ANOVA multiple comparison test was used to verify any significant difference in the COPs among the four groups (classified by season and type of ASHP water heater). • The Kruskal-Wallis multiple comparison test was used to see if any significant difference exists in the COPs among the four groups. • The results demonstrated significant differences in the mean COPs amongst the four groups. • The one-way ANOVA tests and the Kruskal-Wallis tests gave the same statistical outcomes.

Keywords : Air source heat pump water heater; p-value; significance level; one-way ANOVA test; Kruskal-Wallis test.

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