Evaluation of thermal comfort during showering with system-related temperature fluctuations

Abstract

With the decarbonization of heating sector with temperature-sensitive heat pump, comfort must be considered. For users, comfort is a decisive criterion that can hinder the decision for a supply system using renewable energies. Instantaneous domestic hot water heater pose a particular challenge here, as load changes can easily lead to temperature fluctuations. Therefore, the following study aims to determine the perception of temperature fluctuations during showering and to classify them for an assessment procedure. For this purpose, we carried out tests with 120 persons in a controlled environment. The test subjects showered at their desired temperature and gave direct feedback on imposed temperature fluctuations. Positive and negative changes with different rates of change were examined. We reported clear individual differences in the set desired temperatures as well as in the noticed and tolerated temperature fluctuations. The average desired temperature was 38.5 °C, with a quite large variation of ±5.5 K. While 2 % of the test subjects already noticed fluctuations <0.5 K and found them uncomfortable, for others (≈40 %) deviations of 4 K were still comfortable. Therefore, the resulting evaluation was based on a proportion of dissatisfied subjects according to the procedure described by the ISO 7730. This study represents a first step towards the introduction of standardized assessment of instantaneous water heaters and the comfort criteria would allow a comparison of control quality for different applications.