Water Cooled Condenser
When discussing the air-cooled condensers, it was mentioned that the ambient air temperature would affect the efficiency of the unit. The higher the ambient reaches over the design temperature, the more inefficient the unit becomes. For this reason, water-cooled units have made their entrance. Of course the water-cooled condenser has many advantages along with its disadvantages. Some areas use water-cooled units in residences and light commercial units. I cover it here for your information.
Water is used as the heat transfer medium in place of air. Water flows through a heat exchanger where refrigerants contained in separate piping give up their heat to the water. Figure 15-5 shows how a few typical condensers are constructed. Now that you’ve seen the actual condenser and how it is made, you have to get water to make it operate.
In making a selection of whether to use air-cooled or water-cooled, the source of water should be studied very carefully. Water can be secured from a well, city, seawater, brackish, lake, pond, man-made pond. You can see there are many options; however, the content of the water is very important. The reason is that you don’t want a constant battle to keep the condenser clean from minerals or rust. A very rapid buildup on the inner surfaces that causes an inefficient heat exchange is costly to maintain. An air-cooled condenser might be advisable in such a case, or perhaps a water treatment system that would be cost effective. In many areas where an apartment complex or a condominium complex uses a community tower, the maintenance fee is not too high if chemical treatment administered through the water tower is done on a regular schedule to keep the individual condensers located in the individual apartments clean. The individual air conditioning units might range in tonnage from two to five tons. It might be necessary for you to be aware of how the water works.
In Fig. 15-6 a tube-in-tube type condenser is shown. It is very common in residential package units. The package can be rucked away neatly in a closet where it hooks up to a common water riser that is usually built into the wall. All the apartments located above and below use the same riser. Each apartment has a set of valves on the main riser in the event the unit must be removed; the water valves can be closed. What happens when a water valve doesn’t close completely? Never, never, never cut a pipe until you are sure the valve is holding. If it doesn’t, you might be emptying a community water tower all over some expensive carpeting in someone’s apartment, as well as that in apartments below. If a valve doesn’t hold, it will be necessary to find the shut-off valves for the entire riser. The drain valves somewhere below till then have to be found in order to drain the riser so that new valves can be installed. It is always good policy to try and get all the owners on that riser to agree to renew valves at the same time. You might want to turn the whole thing over to another service company.
In water-cooled condensers, some are sealed and some are built with bolted end plates that enable a technician to service it. The sealed condenser such as the tube-in-tube is cleaned with the aid of an acid circulating pump. Both inlet and outlet sides of the water circulating circuit of the condenser are opened. Fittings are placed on both sides to accommodate water hoses. One end of one hose is placed in the inlet fitting, and the other end of the same hose attaches to the discharge side of the acid circulating pump. Figure 15-7 shows a typical acid circulating pump. The pump is set into a five gallon plastic pail. The other hose is attached to the outiet side of the condenser and the other end of the hose is laid into the bottom of the pail. A gallon of sulfuric acid is placed into die pail and circulated through die condenser. The same acid can be used again, but the acidity should be tested often with litmus paper. If the acid level drops, more acid should be added. In using this cleaning procedure, make sure there is plenty of ventilation. You might need a small fan to remove fumes. This procedure is continued for about an hour. It helps eliminate mineral deposits that insulate the condenser and hinder heat transfer. High head pressure is one of the symptoms of a possible condenser problem. Figure 15-8 is another type of sealed condenser called coil-in-shell. It too is cleaned the same way the rube-in-tube is cleaned.
Figure 15-9 is a tube-in-shell condenser. This type unit is used in refrigeration and air conditioning equipment from small tonnages up to very large units. Cleaning this type is more difficult to do. This condenser is constructed with end plates that are designed to be removed for cleaning. A long rod is used, something similar to a ramrod used in rifle cleaning. A wire brush is attached to the end of the rod. With the aid of an electric drill (usually a 3/4-hp slow speed drill is used) each tube of the water circuit is cleaned. After the brush is placed through the tube, it is flushed with water. By holding a light at one end and looking down the other (again as in cleaning a gun barrel), one can see mineral or other deposits. The same tube might have to be reamed and flushed with water several times before the deposits break loose.
A quick way to check the efficiency of the condenser is to touch the water outlet side and the refrigerant (liquid) outlet side of the condenser. The refrigerant should feel warm, not hot. The water outlet should also be warm to the touch. If the outlet water pipe is cold, either too much water is flowing through it or there is no heat transfer taking place. If the outlet pipe is very hot, there is a restriction in the water supply.