Page 346 - Handbook of Energy Engineering Calculations

indirect system expansion-tank volume: 12 percent of collector fluid loop;
controller turnonΔT: 15 to 20°F (27 to 36°C); controller turnoff: 3 to 5°F (5.4
2
to 9°C); system operating pressure: provide 3 lb/in (20.7 kPa) at topmost
collector manifold; storage-tank insulation: R-25 to R-30; mixing-valve set

point: 120 to 140°F (48.8 to 59.9°C); pipe diameter: to maintain fluid
velocity below 6 ft/s (1.83 m/s) and above 2 ft/s (0.61 m/s).
Most domestic solar hot-water heaters are installed to reduce fuel cost.
Typically, domestic hot water is heated in an oil-burning boiler or heater. A

solar collector reduces the amount of oil needed to heat water, thereby
reducing fuel cost. Simple economic studies will show how long it will take
to recover the cost of the collector, given the estimated fuel saving.
A welcome added benefit obtained when using a solar collector to heat

domestic water is the reduced atmospheric pollution because less fuel is
burned to heat the water. All combustion produces carbon dioxide, which is
believed to contribute to atmospheric pollution and the possibility of global
warming. Reducing the amount of fuel burned to heat domestic water cuts the

amount of carbon dioxide emitted to the atmosphere.
Although reduced carbon dioxide emission is difficult to evaluate on an
economic basis, it is a positive factor to be considered in choosing a hot-
water heating system. With greater emphasis on environmentally desirable

design, solar heating of domestic hot water will receive more attention in the
future.

DESIGN OF PASSIVE SOLAR-ENERGY HEATING

SYSTEMS FOR BUILDINGS

A south-facing passive solar collector will be designed for a one-story

residence in Denver, CO. Determine the area of collector required to maintain
an average inside temperature of 70°F (2l°C) on a normal clear winter day for
a corner room 15 ft (4.6 m) wide, 14 ft (4.3 m) deep, and 8 ft (2.4 m) high.
The collector is located on the 15-ft (4.6-m) wide wall facing south, and the
2
2
14-ft (4.3-m) sidewall contains a 12-ft (1.11 m ) window. The remaining
two walls adjoin heated space and so do not transfer heat. Find the volume
and surface area of thermal storage material needed to prevent an unsuitable