MTS Water Quality Guide - Manual (Page 5)

Heat Exchanger Care and Water Quality Guide Heat Exchanger Care 5
Heat Exchanger Care
MTS hydraulic power units (HPUs) are equipped with heat exchangers that are
designed to remove 100% of the HPUs heat load.
Heat exchangers usually provide a long service life with little required
maintenance because they have very few or no moving parts. Often, however, the
heat exchanger is a neglected component of the HPU until it fails. A heat
exchanger failure can result in a costly and time-consuming cleanup, especially
when your cooling water supply is mixed with hydraulic fluid. Proper
maintenance is therefore essential to maintaining a long life for your heat
exchanger. The information that is provided below will help you get the longest
possible service from your heat exchanger.
What is a heat exchanger?
A heat exchanger is a mechanical device that is used to transfer heat from one
medium to another. The amount of heat transferred is directly proportional to the
temperature difference between the hydraulic fluid and the cooling medium.
MTS uses two types of heat exchangers: hydraulic fluid-to-water or hydraulic
fluid-to-air.
Hydraulic fluid-to-
water
Hydraulic fluid-to-water heat exchangers are used in an HPU when an ample
cooling water supply is available. Hydraulic fluid-to-water heat exchangers, also
referred to as oil coolers, use heat transfer to cool the hot hydraulic fluid in the
HPU by passing it over or through a conductor that separates the hydraulic fluid
from the cooling water.
The two most common designs are the plate design, and the shell and tube
design.
Plate design
In the plate design, the hot hydraulic fluid passes between a series of copper-
coated, corrugated stainless steel plates. The herring bone design of the
corrugations in the plates increases the turbulence in the fluid to maximize the
transfer of heat. Cooling water passes between altenating plates to effect the heat
transfer.
Shell and tube design
In this design, the hot hydraulic fluid circulates through the shell and over the
outside surface of a bundle of tubes. Baffles direct the hydraulic fluid through the
shell side of the unit at right angles to the tube bundle. Cooling water passes
through the inside of the tubes and the heat is exchanged from the hot hydraulic
fluid to the cool water. Heat is removed from the water by passing it through a
cooling tower or an evaporation pond.
Shell and tube hydraulic fluid-to-water heat exchangers are available in many
design variations. The straight tube design with a fixed tube bundle is used by
MTS. These units are available with various baffle arrangements to create single
or multiple pass heat exchangers. Multiple pass designs use less water and can be
used more efficiently and at less cost when colder circulating water is available.
The tubes are accessible from either end for cleaning.
Hydraulic fluid-to-air
Hydraulic fluid-to-air heat exchangers, also referred to as air coolers, are similar
to the cooling system in an automobile. Hydraulic fluid-to-air heat exchangers
are used in locations that do not have a sufficient water supply for cooling.
Hydraulic fluid passes through a radiator while air is blown over the tubes and
cooling fins to remove the heat.