Comfort Assessment of Tankless Water Heaters: Review and Suggestions
Abstract
As DHW modules contain only a little amount of potable hot water, which is exchanged very often, they offer the possibility to deliver hygienic potable hot water at lower temperatures and to save energy due to lower temperatures. The assessment of comfort of DHWM is one important aspect, as user acceptance is necessary for the dissemination of DHHM. The paper presents the state of the art and suggests some improvements. First, is to use a comfort index that quantifies the usable share of the drawn heat of the first 60 s after a flow disturbance. This simplifies the comparison between different products. Second, is to consider both, absolute (±2 K) and derivative (±0.1 K/s) thresholds as comfort criteria. For this, it is suggested to use a mathematical pipe model with wall capacity that is reproducing the stretching and the damping of the temperature fluctuation.