Refrigeration Requirements for Precooling and Fermentation Control in Wine Making

Abstract

A database is provided which can be used as a guide to determine the maximum refrigeration capacity required during wine making (precooling and fermentation control). Factors such as maximum daily grape intake, temperature of the grapes, precooling period, fermentation rate, heat gain in the fermentation building, heat gain in the refrigerated water distribution system as well as the efficiency of refrigeration systems are considered. Graphs, as well as equa-tions, are provided from which the maximum refrigeration capacity required for grape intakes varying from 25 t -1 000 t per day can be determined in kJ/h. Provision is made for three different precooling periods. Separate graphs are provided from which the influence of the temperature of the grapes, as well as the influence of heat gain in re-frigerated water distribution systems on the overall refrigeration capacity required, can be determined respectively. The database cannot replace thorough detailed refrigeration system design and engineering. However, it provides wine makers with a simple guide whereby designs can be checked, or the use of the capacity of existing systems man-aged more effectively. Vergunst (1971) determined the refrigeration capaci-ty required for a winery with a daily juice intake (5d/week) of 171 450/, precooling from 26°C-15°C over a 22 hour period and fermenting from 22° Balling to dryness with-in 6 days (3.6°B.d l). For calculation purposes, Ver-gunst assumed a heat gain of 15%. Unfortunately, it is difficult to use these figures as a basis from which to cal-culate the refrigeration capacities required for wineries where conditions differ from those used in this ex-ample. The calculation of load and the determination of heat gain (refrigeration loss) under varying conditions are critical for the correct sizing of new refrigeration plants, as well as for the efficient management of the refriger-ation capacity of existing plants. Factors such as maxi-mum daily grape intake, temperature of the grapes, length of precooling period, fermentation rate, heat gain in the refrigerated water distribution system, heat gain in buildings or tanks and the efficiency of the re-frigeration system are important. However, very little information correlating these factors is available. The object of this paper is to provide a simple but ef-fective database which can be used as a guide to deter-mine the maximum refrigeration capacity required dur-ing wine making (precooling and fermentation control). A cellar crushing a total of 10 000 t of grapes over a period of two months (40 working days), does not crush \0 000/40 = 250 t/day. Invariably a peak is experienced