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).

Heat Exchanger Specifications

SunEarth Model Number	Width (in)	Height (in)	Capacity Sizing (sq. ft. collector per plate)	Plate Capacity	Depth (in)	Connections	Max Pressure (psig)
SPL31	4.8	11.3	9.0	10-150	0.36+0.09NP	1", 1-1/2"	232
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.

 

Closed-Loop Glycol	Drainback

Sizing SunPlate Units for Commercial Arrays

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.