Summary
In this chapter, we covered hydronics systems, systems involving the flow of steam or water to transfer heat or cooling from one place to another.
Steam Systems
Principal ideas of this section include: how steam is used; its behavior as a gas and how it condenses as it gives up its latent heat; how the resultant conden- sate is drained out of the steam pipes by traps and then returned to the boiler, to be boiled into steam again.
Water Systems
In this section we described water systems and the economical direct arrangement and the more costly, but largely self-balancing, reverse-return piping arrangement. Once a system has been designed, the design flow and head are known and can be plotted on the same graph as the pump curve, to find the expected operating condition.
Hot Water Systems
From general water systems, we moved into hot water systems. The use, and energy savings of variable speed pumps was introduced. This was followed by a discussion of how two pumps in parallel can be used to provide reduced energy consumption for most of the heating season, as well as substantial, automatically-available, stand-by capacity should a pump fail.
Chilled Water
Because chilled water systems need constant water flow through the chiller evaporator, the economies of variable flow can be achieved through decoupled and distributed piping arrangements.
Cooling Towers
Cooling towers were described as well as the difference between open and closed water systems. The hot water and chilled water circuits are normally closed systems, but the cooling tower is an open system. The open system has a modified design requirement, since the pump must not only overcome the friction, head, to flow around the circuit, but must also provide lift to raise the water from the balance point to the highest point in the system.
Bibliography
1. ASHRAE Course Fundamentals of Water System Design
2. 2004 ASHRAE Handbook Systems and Equipment
3. 2001 ASHRAE Handbook Fundamentals