Simplifications have been made to ensure that calculations of energy consumption and environmental impact are readily understandable. These simplifications may not represent actuality in a particular system, but this approach does allow a realistic comparison to be made because the same conditions are applicable to each case. Differences arising from the nature of the system, refrigerant and compressor type are varied according to the case.
Seasonal operating conditions
A condensing temperature of 25°C has been used to represent average operating conditions in Northern Europe, and 30°C for Southern Europe (see “Climate”, below).
The default MT load is 75kW and the LT load is 25% of this value. The loads may be varied by the user. Loads are assumed to be constant throughout the year. For Cascade and Secondary systems the MT load includes LT system rejected heat.
Suction line losses and pressure drops are ignored.
The average HFC condensing temperature of 25°C representing Northern Europe conditions is based on an average outdoor temperature of 15°C with a condenser temperature difference of 10K. This is with condensing temperature controlled at 20°C minimum, and therefore with all ambient temperature hours below 10°C counting as 10°C. Consultation over temperature profiles for a number of Northern European cities has revealed that, on this basis, the average ambient temperature is between 14 and 16°C, and so 15°C is a good average. This has been done using a seasonal BIN analysis, splitting the annual outdoor temperatures into segments (bins). The loads and energy consumptions for all segments are added together. The ratio of these totals is the Seasonal COP and it has proved to be almost identical to the selected value at 25°C condensing.
A typical city in Southern Europe would have an average ambient temperature of 18 to 20°C. In this study, 30°C average condensing temperature has been taken as the representative temperature of Southern Europe, based on the same approach as for Northern Europe.
The model considers the refrigeration system of a typical European supermarket. The equivalent continuous default loads are: MT 75kW and LT 18.75kW. These values value may be changed by the user.