Experimental investigation on the dynamic characteristic of the direct expansion solar assisted ejector-compression heat pump cycle for water heater

A continuing research on the direct expansion solar assisted ejector-compression heat pump cycle for water heater is presented in this paper, aiming to reveal the system dynamic characteristic by experimental method. The performance advantage of the presented system is verified at first. According to the test results, under the considered condition, the presented system can outperform the traditional ejector enhanced heat pump system and the air-source heat pump system by 24.1% and 29% in the heating coefficient of performance aspect, 24.2% and 30.5% in the average heating capacity aspect. After that, the main parameters affecting the dynamic behavior of the presented system are examined, including the ejector nozzle exit position, ejector mixing chamber diameter and solar radiation intensity. According to the test results, the system achieves the maximum heating coefficient of performance and heating capacity under mixing chamber diameter of 4 mm and nozzle exit position of 6 mm. Note that the ejector malfunction phenomenon appears when the mixing chamber diameter is reduced to 3 mm, due to the blocked flow channel of the ejector secondary flow. Additionally, the experiment finds that enhancing the solar radiation can obviously improve the ejector pressure lift ratio and help the system achieve superior heating performance.