ชื่อประเทศ
The heat exchanger consisted of a 15 mm diameter copper
tubes placed inside the solar collector, 100 mm below the glass
and 100 mm above the absorber plate. The heat exchanger consisted
of 70 tubes covered the whole area of the drying collector.
These tubes were fixed and put over a metal holder of width
20 mm at each side of the solar collector. Two ends of the copper
tubes were connected to the water storage tank with 15 mm plastic
tubes. The capacity of the water tank was 500 l. Water flew from
water tank and circulated through the plastic and copper tubes by
a small water pump of capacity 20 l/h. The heat exchanger gave a
part of the heat collected during the hours of the sun-shine, which
was carried by air inside the solar collector, to the water inside the
copper tubes. The water passed very slowly inside the pipes to be
able to take the largest part of heat carried in the air contact with
the external surface of the tubes. This water was stored inside a
plastic tank of 500 l volume and insulated by 50 mm fibre-glass.
The heat stored during the day in the water tank could be used
again at night. The temperature of this water could be raised by
using 6 kW water heaters located inside the tank to reach a desired
temperature for drying during the night as well as in adverse
weather for maintaining the temperature and the humidity
throughout the drying process.