Handbook of air conditioning and refrigeration / Shan K

8.24 CHAPTER EIGHT
FIGURE 8.7 A two-pipe individual-loop low-temperature hot water heating system for a factory.
Finned-Tube Heaters
space by the air conditioning system that cools the conditioned space in summer. In locations
of cold climate, if only winter heating is required, then a separate outdoor ventilation system
sometimes is required instead of opening the windows manually. Outdoor ventilating systems are
discussed in Chaps. 23 and 24.
The design procedure for a hot water heating system involves the following:
● Calculation of the space heating load, as discussed in Chap. 6
● Selection of suitable finned-tube heaters
● Division of the heating space into various control zones, or individual loops
● Planning of a piping layout, containing branches and necessary piping fittings
● Location of the boiler, circulating pumps, air separator, and expansion tank in the mechanical
equipment room, and determination of their capacities
● Specification of the control functions of the capacity and safety control systems, including the
sequence of operation
A finned-tube heater is a terminal unit installed directly inside the conditioned space to deliver heat
energy to the space by means of radiation and convection. A finned-tube heater consists of a finnedtube
element and an outer enclosure, as shown in Fig. 8.8. The tubes are often made of copper and
steel. Copper tubes are usually of 0.75-, 1-, and 1.25-in. (19-, 25-, and 32-mm) diameters, and steel
tubes of 1.25- and 2-in. (32- and 50-mm) diameters. For copper tubes, fins are often made of aluminum.
For steel tubes, the fins are made of steel. Fin spacing varies from 24 to 60 fins per foot (79
to 197 fins per meter). A finned-tube heater may have a length up to 12 ft (3.6 m).