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Chapter 4
Outlet duct UA is the overall loss coefficient-duct area product for the duct carrying air from the
collector array. This parameter is used only if Yes has been selected for duct losses.
Percent duct leak rate is the percent of the collector outlet duct flow rate which is leakage. The
collector is assumed to be under negative pressure, i.e., all leaks are into the ducts rather than
out. This parameter is used only if Yes has been selected for duct losses.
Domestic hot water (Yes/No) toggles to indicate whether a solar domestic water heating system
is part of the heating system. If Yes is selected, a solar domestic hot water system is
considered in addition to the space heating system. The following 6 parameters are then used
to describe the domestic water system. If No is specified, the following 6 parameters are
ignored. The liquid storage system should be selected if air collectors and a water-to-air heat
exchanger are used to supply only domestic hot water.
Daily hot water usage is the average amount of hot water per day required at the set
temperature. Monthly values are allowed. This parameter is visible only if Yes has been
selected for domestic hot water parameter.
Water set temperature is the temperature to which domestic water is to be heated. Monthly
values are allowed. This parameter is used only if Yes has been selected for domestic hot
water.
Environment temperature is the temperature of the surroundings of the domestic water storage
tank to which heat losses occur. Monthly values are allowed. This parameter is used only if
Yes has been selected for domestic hot water.
UA of auxiliary storage tank is the product of the energy loss coefficient and surface area for
the auxiliary tank in the solar domestic water heating system. In a single tank system, use the
tank surface area above the heating element thermostat. This parameter is visible only if Yes
has been selected for domestic hot water.
Heat exchanger water flow rate is the mass flow rate of water from the solar preheat tank to the
air-water heat exchanger, used only if Yes has been selected for domestic hot water.
Air-water heat exch effectiveness is the ratio of the actual heat transfer rate to the maximum
possible heat transfer rate for the air-to-water domestic hot water heat exchanger. This
parameter is used only if Yes has been selected for domestic hot water.
The thermal performance is calculated on a monthly basis. The output (in English units) for the
default parameters with 26 flat-plate collectors and cp =0.24 appears below.
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