Experimental investigation of temperature and flow distribution in a thermosyphon solar water heating system

Natural circulation solar water heating systems are available in varying collector geometries (and materials), storage tank capacities and specifications of individual components. Though theoretical and experimental studies including the test procedures are available to estimate the performances of these systems, detailed experimental studies showing the temperature profiles of the absorber plate, water temperature in the riser and water flow in the riser are few. This paper presents details of experimental observations of temperature and flow distribution in a natural circulation solar water heating system and its comparison with the theoretical models. The measured profile of the absorber temperature near the riser tubes (near the bottom and top headers) conforms well with the theoretical models. The values at the riser tubes near the collector inlet are found to be generally much higher than those at the other risers on a clear day, while on cloudy days, these temperatures are uniform. The mean absorber plate and mean fluid temperature during a day has been estimated and compared with theoretical models. The temperature of water near the riser outlets was found to be fairly uniform especially in cloudy and partly cloudy days at a given plane during a day. The temperature of water in the riser depends on its flow rate. Measurements of glass temperature were also carried out.