What do Pump Pros Know and why do they know it? This series of articles highlight the brilliance of those who work with pumps.
Pumps are Critical for Keeping Us Comfortable
Whether it’s heating or cooling, pumps play an essential role in climate control.
Climate control systems make use of many different sizes and designs of pumps. Whether it’s heating and cooling in your car, home, office, or factory, pumps are essential to effective and reliable climate control.
Heating and Cooling Systems in General
Most climate control systems use fans, blowers and compressors in the heating and cooling process, and many systems also use liquid pumps to circulate water or some other heat transfer fluid through a system.
Vehicles, homes, and commercial and industrial buildings use very different types of climate control systems, but they all work on the same principle: they transfer heat from a warmer environment to a cooler one. Most of this is done through a heat exchanger. A familiar type of heat exchanger is a radiator in a car. A water pump pushes hot water out of the car’s engine through a hose and into the top of the radiator. The hot water then flows down through dozens of small tubes in the radiator, and ambient air flow over the radiator and around the tubes to cool the water inside the tubes, and the cooled water flows to the bottom of the radiator, where it is pulled back into the engine by the water pump through a second hose.
Hot Water Systems
Many buildings—including residences and commercial and industrial buildings—use hot water heating systems that work similarly to this. A boiler heats water using natural gas, propane, fuel oil, or electric coils. The water in a boiler often does not “boil” and remains liquid as it is delivered for heating, but some are designed to generate steam, which is used for heating. Larger systems—such as those in commercial buildings—often use a pump to route fuel oil from the fuel tank to the boiler.
A pump then circulates hot water from the boiler through a network of pipes to individual rooms in the building. The pipes are covered by hundreds of thin metal fins that are heated by the water in the pipe, and the heat transfers from the hot fins to the air in the room.
The water becomes cooler as heat transfers from the water into the room. Essentially, then, the heat is exchanged from the water to the fins to the room air. The cooler water then returns back to the boiler, where it is reheated and sent back though the building by the circulating pump.
Climate Control Systems in Vehicles
Heating systems in cars and other vehicles do not rely on a boiler as a source of heat. Instead, the car’s gas or diesel engine produces more than enough heat to keep the passenger cabin warm. The vehicle’s water pump circulates water throughout the engine and into the radiator to keep the engine cool and also pumps hot water from the engine into the passenger cabin.
This hot water flows into a second, much smaller heat exchanger in the passenger cabin. This small heat exchanger is generally called a heater core, and a fan pumps air from within the cabin through the heater core and back into the cabin.
Heating and cooling systems usually share some of the same controls, fans, and some of the in-cabin ductwork. The ductwork serves as channels to route heated or cooled air from the different areas of the cabin, such as the floor and dashboard. When cooling is called for, a diverter routes air pumped by the fan past the heater core and through the evaporator (cooling core). Likewise, when heat is needed, the diverter valve directs air through the heater core, but not the evaporator.
Climate control systems for commercial and industrial buildings are often quite similar to those used in residential applications—at least for small facilities. Large and multistory buildings present the challenge of distance. A residential forced-air climate control system can heat or cool the air in a central location, then use a powerful fan to pump the air throughout the home. This would be impractical in a commercial environment because the air would cool down or warm up over long distances traveled to individual offices or workstations. On the other hand, it would be impractical to place multiple heating and air conditioning units throughout a building.
The solution that has worked well for decades is to place centralized heating and cooling system in a building’s cellar, on its roof, or in a nearby enclosure. Instead of heating or cooling the air directly, these systems typically heat or cool water or some other heat-transfer fluid. A powerful pump then routes the water through insulated pipes throughout the building to provide heating or cooling. Valves placed at strategic locations throughout the system regulate how much water flows to each floor or section of a floor in delivering the proper amount of heating or cooling.
Extremely tall buildings often use one or more booster pumps to avoid having to pump water at extremely high pressures. Water can generally be considered to weigh about 64.4 lb/ft3. So, 1-ft column of water produces a static pressure of 0.433 psi. Each story of a commercial building is roughly 10-ft tall, so pumping water to the top of a floor requires the pump to accommodate 4.33 psi. So, a 40-story building would be required to produce a static pressure of 173.2 psi. To avoid having to use a high-pressure pump and piping, a booster pump could be placed at the 20-story level to reduce the maximum pressure to 86.6 psi.
Refrigerant in these large systems often evaporates in a chiller heat exchanger that cools water instead of room air. After leaving the heat exchanger, the refrigerant then flows to the compressor, then to the condenser, which may be cooled by air or water. The chilled water eventually returns from the building but has picked up heat.
As with residential systems, the system may also operate as a heat pump to cool the circulating water during hot weather and heat the water during cold weather. In any case, the pump that circulates the water is an essential component for the successful operation of the system.