Gore Multi-Sports Complex
Solutions
Construction
Base of ice rink
Freezer unit
Achieving simultaneous –9 and +45°C flow temperatures with an affordable 'off the shelf' chiller
Two independent control systems have been provided, one for the coolant temperature and one for the heating circuit temperature. The coolant temperature is controlled by the requirement of the ice temperature and is manually adjustable to suit the activities. The heating circuit is controlled by two sequential control loops. If the heating circuit temperature is too high, the heat rejection dry cooler will run. If the heating circuit temperature is too low, the heat pump coil at pool exhaust air will be used to draw more heat to the system.
Maximising use of coolant and stable operation of the cooling plant
A cascade coolant circulation system maximises the cooling effect of the coolant, and creates an overall coolant temperature difference of 4 to 5°C. This allows the total flow rate of the coolant to be reduced substantially by as much as 70%. The evaporator of a standard “off the shelf" chiller can now be used avoiding excessive pumping and cooling energy usage. As the chiller is operating sufficient temperature difference, no special coolant supply temperature control is necessary.
Making best use of low grade heat
A characteristic of heat pump heating systems is that the temperature of the heating media is relatively low, 40 to 45°C, comparing with 80°C commonly available with boiler heating. The use of lower heating circuit temperature will increase the efficiency of the heat pump system. With the low grade heat, the supply air temperature is limited to not more than 32 to 35°C depending on the heating medium temperature at the time. Although it is possible to design a heating coil to achieve a higher air temperature with the low grade heat, the much higher air resistance of the deep coil will significantly increase the fan power requirement. The challenge is to achieve the highest temperature air using the low grade heat, thus reducing the total air flow to meet the heating demand. High air flow rate will significantly increase the energy usage.
