KeepRite K40-CU-IM-13, Инструкция по установке и обслуживанию

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17
Water-Cooled Condensers
WARNING
All water and drain connections to the unit must be made in accordance with national as well as local plumbing
codes and by-laws.
Cooling water circuits in some shell and tube water-cooled condensers may be either series or parallel as
required by the particular application. The “series” flow is usually for city water where lower entering water
temperatures exist and higher-pressure drops can be tolerated (such as city water supplies). The “parallel”
circuit flows are usually required when the water temperatures enter at 85
o
F (29.4
o
C) or higher requiring lower
water pressure drops (such as closed loop cooling tower supplies).
On some condensers, the
water circuiting may be
entirely internal with only an
inlet and outlet water fitting.
The water inlet is always at
the bottom connection.
All water-cooled condensers
require a water regulating
valve that must be installed
upstream of the condenser.
The water-regulating valve is
adjustable and is set to
provide the desired condensing pressure. As the condensing pressure rises, the valve will open and allow more
water to flow. As the condensing pressure lowers the valve will start to close to reduce the amount of water flow
into the condenser. If water supply pressure is excessive, a pressure-reducing valve must be used since the
allowable working pressure of water valves and condensers is normally 150 psig (1136 kPa). Typical
condensing temperatures normally range between 90 to 110
o
F. The actual water inlet temperature and water
supply flow capacity available at the site determines the suitable condensing temperature. Lower inlet water
temperatures (below 70
o
F) allow the condensing unit to run at a lower condensing temperature without resulting
in a high water flow rate (consumption). Higher water inlet temperatures (above 85
o
F) require the condensing
temperature to be higher to avoid excessive water flow rates. Refer to the water flow rate chart to estimate the
flow rate (GPM-US gallon per minute) at given water temperatures and loads. The TD (temperature difference)
is the difference between the condensing temperature and the water inlet temperature.
Example: Given 80
o
F inlet water available, +25
o
F evaporating temperature application and 1 ton (12,000Btuh)
evaporator load. The results are:
20
o
F TD = 100
o
F Cond.Temp., series flow is .148 x 12 = 1.78 GPM, parallel flow = .185 x 12 = 2.22 GPM
30
o
F TD = 110
o
F Cond.Temp., series flow is .103 x 12 = 1.24 GPM, parallel flow = .128 x 12 = 1.54 GPM
Knowing the GPM you can estimate the pressure drop through the condenser (and compressor, if with body
coil). Refer to the Typical Pressure Drop tables and use the appropriate flow to estimate the resulting pressure
drop. If using a condenser that has only ONE water circuit (two connections) use the “parallel” column on the
GPM flow rate chart.
Care should be exercised in locating the condensing unit so that the condenser will never be exposed to
temperatures below freezing.
Excessive water velocities or cavitation on the waterside of the condenser tubes may damage a water-cooled
condenser. In order to prevent operating difficulties, care should be taken to follow the instructions outlined
below:
(a)
Water velocities through the condenser should not exceed 7 fps (2.13 m/s). Higher velocities can result
in “impingement corrosion”. In order to maintain water velocities at an acceptable level, parallel circuiting
of the condenser may be necessary when high water flow is required.
(b) If a water-circulating pump is used, it should be installed so that the condenser is fed from the discharge
side of the pump.