20
16
-0
4-
29
The maximum allowable connection loads given below are valid
for low cycle fatigue. If high cycle fatigue is involved, a special
analysis should be carried out. The following limits for moment
should not be exceeded.
Max. Bending moment
Torque moment
Connections
20 Nm
70 Nm
Maximum moments onto connections
System assembly
The Cross 30 may be installed as a single module or in a system
including several Cross 30 units. In systems, the Cross 30 units
can be mounted in parallel or serial configuration for liquid flow
and gas flow. To obtain the calculated performance, it is im-
portant that heat exchangers are installed in accordance with
the configuration in AirecCalc. See the calculation report. Note:
Wrongly installed piping will jeopardize the performance of the
installation.
Flow direction may be:
Cocurrent
= fluids flow in the same direction through the heat
exchanger
or
Countercurrent
= fluids flow in opposite directions through the
heat exchanger.
Countercurrent Cocurrent
Housing the Cross
The Cross design has open sides to allow gas to enter and
leave. It must have a housing to be functional. The Cross heat
exchanger must be mounted in the housing according to the
Cross design guidelines.
When mounting the Cross in the housing, treat the heat
exchanger with care. Do not use excessive force, or bend or
weld the heat exchanger. Never expose the housing to
excessive pulsations (i.e. cyclic pressure or temperature
changes) or vibrations, because there is a risk that these are
transferred to the Cross heat exchanger unit. If there is any risk
of excessive pulsation or vibration, install vibration absorbers /
muffler on the housing.
The water connections should not be directly welded to the
housing, because thermal expansion may cause severe damage
to the heat exchanger. Material deformation due to differences
between the internal and external pressures may also damage
the heat exchanger
.
Operating conditions
The Cross is used with a liquid on the circuit with connections
and a gas on the open side. The heat exchanger must operate
in line with approved design parameters: temperatures,
pressures and flow rates.
Liquid side
Typical medias are ethylene/propylene glycol, thermal oil, water
or other liquid non-corrosive to stainless steel. It is important
that the liquid is of good quality without contamination or
corrosive substances. The medias should not contain particles
or any other undissolved matter, we recommend that a strainer
with a size of 16-20 mesh (
number of openings per inch)
is
installed before the Cross 30. The particles could otherwise
block the channels, causing bad performance, increased
pressure drop and the risk of boiling.
Systems with water or another evaporating liquid must be
equipped with the necessary bleed valve mounted in a position
higher than the heat exchanger. Air/gas inside the liquid
channels will reduce heat transfer and water circulation, which
also could cause boiling.
The liquid flow must be constant and with sufficient pressure to
keep its evaporating/boiling temperature above the plate
temperature. Local evaporation/boiling will adversely affect
heat transfer and water circulation, and may lead to a risk of
serious damage to the heat exchanger. Note: The pressure at
the coolant outlet must be high enough to avoid boiling.
The Cross must always have the cooling fluid circulating fully
before the hot gas enters the heat exchanger.
The coolant must NEVER be allowed to freeze.
Never expose the Cross heat exchanger to excessive liquid
pulsations (i.e. cyclic pressure or temperature changes).
Gas side
The gas media should not be corrosive to the heat exchanger.
The gas flow must be started after, or simultaneously to, the
start of the liquid flow. If the liquid flow is interrupted, the gas
must be stopped or caused to by-pass the Cross heat
exchanger to avoid boiling on the liquid side.
The Cross heat exchanger must not be operated in such a
manner that stagnant condensate is allowed to accumulate.
Never expose the Cross heat exchanger to excessive gas
pulsations (i.e. cyclic pressure or temperature changes).
The heat exchanger must NEVER be operated without a coolant
flow.
Operational start-up
Make sure that:
-
If there is a risk of high temperatures, the unit is insulated as
a precaution to avoid injuries.
-
Installation has been carried out according to the flow
schedule / drawing and recommendations.
-
Connections are tight.
-
No vibrations or pulsations are transferred to the Cross 30.
-
The liquid side is filled and deaerated.
-
The flow rate and pressure on the liquid side are correct
before gas flow is started.
-
The temperature and flow rates are according to
specification.
-
There is appropriate drainage to deal with any condensation.
Maintenance
The Cross has no moving parts or electrical components.
The following should be inspected regularly:
-
Operational design conditions for the system being
maintained, and meeting the calculated / design values
(leaving temp., pressure drop).
-
Increased pressure drop and decreased thermal efficiency
over time are signs of possible fouling.
-
Connections for tightness.
-
Gas channels for accumulated dirt.
-
Plate surfaces for corrosion.
-
Seal and gaskets.
-
External components such as valves, dampers and controls.
Gas
Gas
Liquid
Liquid
