Flat Plate Heat Exchangers
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Our flat plate heat exchangers are copper-brazed flat plate heat exchangers constructed
entirely from 316 stainless steel. The plates within the unit are
embossed with a chevron pattern that creates a lattice of interwoven
flow channels to promote turbulent flow. Individual heat
exchangers may contain anywhere from 10 to 200 plates creating a large
number of parallel flow paths for low pressure drops on the order of 2-3 psi.
Stacking of the embossed plates allows for highly compact units that can
pack well over 200 sq. ft of heat transfer surface area in a unit that
has a footprint of only 1.2 sq. ft.
The small footprint of our flat plate heat
exchanger makes
it economical to obtain very effective heat transfer in closed loop
systems on par with open loop designs. Our flat plate heat
exchangers are
available in two footprint sizes: the SPL31 and the larger SPL110.
The smaller SPL31 contains up to 150 plates and the SPL100 has a capacity
of 200 plates. Both units are available in 10 plate increments and
come standard with male NPT fittings (sweat fittings may be custom
ordered).
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SunEarth Model Number |
Width (in) |
Height (in) |
Capacity
Sizing |
Plate Capacity |
Depth |
Connections |
Max Pressure (psig) |
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SPL31 |
4.8 |
11.3 |
9.0 | 10-150 | 0.36+0.09NP |
1", 1-1/2" |
232 |
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SPL110 |
9.8 |
18.2 |
50.0 | 30-200 | 0.39+0.09NP |
1-1/2" |
232 |
Typical Applications
Our flat plate heat exchangers are typically used in double pumped
configurations for commercial scale glycol or drainback systems.
Our flat plate heat exchangers offer higher performance and typically lower cost than
immersed tube bundles for larger commercial scale systems.
Although the requirement of a potable side pump adds to mechanical
complexity, our flat plate heat exchangers can boost collector output by 10-15% over
immersed bundles by dropping the collector loop temperature closer to
the temperature of the storage tank. Although this increased
output may not outweigh the added cost and complexity of the pump in
smaller installations, the higher output in larger systems often
outweighs the disadvantage of the second pump.
Arrays of anywhere from 2 to 240 collectors can
be accommodated with the two frame sizes of the SPL31 and SPL110.
Because of their extremely compact size, the units have very low heat
losses and do not need to be insulated. Additionally, the heaviest
SPL31 weighs only 48 lbs. and the heaviest SPL110 is 190 lbs. meaning that
they can be wall-hung to minimize demands for space in tight mechanical
rooms.
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Closed-Loop Glycol |
Drainback |
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| Sizing SunPlate Units for Commercial Arrays | |
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Sizing of the heat exchanger is critical to overall system performance. If the heat exchanger is undersized then the operating temperature of the collector loop will rise and cause the performance of the array to suffer. On the other hand, oversizing a heat exchanger can mean spending a lot of money for only marginal performance gains. The figure on the left shows how the solar fraction of a typical commercial system is affected by the effectiveness of the heat exchanger. An effectiveness of 1.0 represents 100% efficient heat transfer where the closed loop system performs the same as an open loop system with no heat exchanger. Flat plate heat exchanger sizing guidelines are based on an effectiveness of 0.70-0.80 that provides the optimum balance between system efficiency and unit cost. In this range of effectiveness, the solar fraction is only 2-4% less than that of an equivalent open loop system. |
Example: Array of 24 EP-40 Collectors
At 40.8 sq. ft. gross area per collector, 24 EP-40's have a total array area of 979.2 sq. ft. Referring to the heat exchanger specifications in the table above, we see that the each plate in an SP31 can handle 9 sq. ft of collector and each plate in the SP110 can handle 50 sq. ft. Therefore, we would need either 108.8 (979.2/9) plates for the SPL31, or 19.6 (979.2/50) plates for the SPL110. Because the units come in 10 plate increments we would round the numbers up to 110 plates and 20 plates respectively. Since the minimum number of plates in the SPL110 series is 30 we would opt for the SPL31 series with 110 plates for which the part number would be SPL31-110.