Development and validation of a method for testing and rating thermosyphon solar water heaters

In 1992, the Solar Rating Certification Corporation (SRCC) added an optional solar water heating system certification and rating protocol, SRCC Document OG-300. This standard includes qualitative and quantitative testing to ensure product safety, reliability and the prediction of thermal performance. Quantitative tests are performed to determine model inputs from which ratings are determined based on computer simulations.; Two complimentary test paths were established in order to determine the computer model inputs: (a) a system test approach in which effective system model parameters are regressed to fit test data and (b) a component test approach where significant system components are evaluated in isolation, and the component results are input into a validated system model. Between these two approaches, all systems could be rated for thermal performance, with expectation that most systems could be quantified under the component test path.; While the system test path has the advantage of being capable of testing any system, it is time consuming and costly. The setup of the entire system, instrumentation, data collection and model parameter regression takes a minimum of 4 weeks, and as long as 12 weeks (depending on weather). Therefore it becomes advantageous to test a system using a component-based model due to simpler testing, less cost, and significantly shorter times for the tests and analyses.; Prior to this work, SRCC has been testing thermosyphon systems using the system test approach only. The modeling was based upon an Australian TRNSYS type that allowed direct and mantle-type thermosyphons only, and applicability to other configurations is uncertain. A new TRNSYS thermosyphon model has been developed previous to this work that uses standard TRNSYS types/algorithms, thus allowing use of standard tank and heat exchanger models. This approach enables rating thermosyphon systems using the component-based method. Type205 is capable of accurately determining the natural convection flow in thermosyphon systems from component measurements, including pressure drop data to increase accuracy of model flow predictions. Prior to implementing this model at SRCC, adequate validation of its accuracy through the collection, analysis and comparison of test data to model predictions is necessary. This work is comprised of the methodology for appropriately testing thermosyphon system components, the evaluation of the accuracy of the models predictions, and the models sensitivity to variations in the annual thermal performance. Based on these findings, preliminary recommendations for a concise test procedure using component-based tests and rating models for thermosyphon systems are given.