Solar radiation is incident on the glass cover of asolar collector at a rate of 700 W/m2. The glass transmits88 percent of the incident radiation and has an emissivityof 0.90. The entire hot water needs of a family in summercan be met by two collectors 1.2 m high and 1 m wide. Thetwo collectors are attached to each other on one side so thatthey appear like a single collector 1.2 m * 2 m in size. Thetemperature of the glass cover is measured to be 35°C on aday when the surrounding air temperature is 25°C and thewind is blowing at 30 km/h. The effective sky temperaturefor radiation exchange between the glass cover and the opensky is 240°C. Water enters the tubes attached to the absorberplate at a rate of 1 kg/min. Assuming the back surface of theabsorber plate to be heavily insulated and the only heat lossto occur through the glass cover, determine (a) the total rateof heat loss from the collector, (b) the collector efficiency,which is the ratio of the amount of heat transferred to thewater to the solar energy incident on the collector, and (c)the temperature rise of water as it flows through the collector.
Solar radiation is incident on the glass cover of a
solar collector at a rate of 700 W/m2. The glass transmits
88 percent of the incident radiation and has an emissivity
of 0.90. The entire hot water needs of a family in summer
can be met by two collectors 1.2 m high and 1 m wide. The
two collectors are attached to each other on one side so that
they appear like a single collector 1.2 m * 2 m in size. The
temperature of the glass cover is measured to be 35°C on a
day when the surrounding air temperature is 25°C and the
wind is blowing at 30 km/h. The effective sky temperature
for radiation exchange between the glass cover and the open
sky is 240°C. Water enters the tubes attached to the absorber
plate at a rate of 1 kg/min. Assuming the back surface of the
absorber plate to be heavily insulated and the only heat loss
to occur through the glass cover, determine (a) the total rate
of heat loss from the collector, (b) the collector efficiency,
which is the ratio of the amount of heat transferred to the
water to the solar energy incident on the collector, and (c)
the temperature rise of water as it flows through the collector.
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