Now principal lecturer in building services engineering at Sheffield City Polytechnic, UK, the author here discusses work previously carried out at the Department of Building, UMIST. It concerned the heat transfer capability of the heat exchanger in the storage cylinder when, as in the summer, a combined system is run at part-load for domestic hot water only. This, it is suggested, is a parameter of fundamental importance. A 14.7 kw output gas-fired boiler serving a 135-litres storage cylinder, with compressed draw-off schedule, was used in tests with four different heat exchangers having surface areas ranging from 0. 18 m2 to 0.88 m2. Recorded efficencies of hot water production ranged from 36.1 to 56.5 per cent, and the proportion of boiler running time to total boiler operation time ranged from 35.2 to 82.9 per cent. Discussing those results, the author relates the heat exchanger capacity to the empirical boiler efficiency expression and attempts to quantify the losses.
Tijdschrift beschrijving