1. Subcooling Mini-Split Senior Capstone Design
Samuel Prentiss
Matt Strong
Bruce Tuttle
Bangor Hydro Presentation
12/17/13

2. Tonight’s Points Subcooling Heat Pump Installation & Testing
Return on Investment
Marketable Product

3. The Heat Pump Cycle R-410A Vapor Condenses R-410A Vapor Compressed
R-410A Liquid Evaporates
R-410A Liquid Expands
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4. Heat Pump – No Subcooling
Saturated Liquid Line
Saturated Vapor Line
𝑸 𝑯 = 𝑸 𝒄𝒐𝒏𝒅𝒆𝒏𝒔𝒆𝒓
𝑸 𝑳 = 𝑸 𝒆𝒗𝒂𝒑𝒐𝒓𝒂𝒕𝒐𝒓
𝑾 𝒊𝒏 = 𝑾 𝒄𝒐𝒎𝒑𝒓𝒆𝒔𝒔𝒐𝒓
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5. Heat Pump – With Subcooling
Qsubcooler
All Saturated Liquid After Passing Through EEV
Qevaporator_additional
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6. Latent & Sensible Heat
Vapor R-410A Condensating is Latent Heat ( ℎ 𝑓𝑔 )
Latent Heat is Constant Temperature
Evaporation is Latent
Liquid R-410A Subcooling is Sensible Heat
Sole Effect is Temperature Change
Superheating is Sensible

7. Subcooler Coil Output

8. What is Coefficient of Performance?
𝐶𝑂𝑃 𝑛𝑜_𝑠𝑢𝑏𝑐𝑜𝑜𝑙𝑒𝑟 = 𝑄 𝑜𝑢𝑡 𝑊 𝑖𝑛 = 𝑄 𝑐𝑜𝑛𝑑𝑒𝑛𝑠𝑒𝑟 𝑊 𝑐𝑜𝑚𝑝𝑟𝑒𝑠𝑠𝑜𝑟 = 3
𝐶𝑂𝑃 𝑠𝑢𝑏𝑐𝑜𝑜𝑙𝑒𝑟 = 𝑄 𝑜𝑢𝑡 𝑊 𝑖𝑛 = 𝑄 𝑐𝑜𝑛𝑑𝑒𝑛𝑠𝑒𝑟 + 𝑄 𝑠𝑢𝑏𝑐𝑜𝑜𝑙𝑒𝑟 𝑊 𝑐𝑜𝑚𝑝𝑟𝑒𝑠𝑠𝑜𝑟 = 4
𝑾 𝒄𝒐𝒎𝒑𝒓𝒆𝒔𝒔𝒐𝒓 Does Not Change!

9. C.O.P. for the Visual Learners
“Without Subcooling”
COP=3 `
“With Subcooling”
COP=4 `

10. C.O.P. Due to Subcooling
At Least 20F Subcooling Needed to be Beneficial

11. Compressor EER

12. Air Outlet Temperature

13. Capstone Plan Build Subcooler Unit (Jan-Feb 2014) Monitor & Improve!!
Install at University Garage (Feb 2014)
1 ton Fujitsu Mini-Split Heat Pump
GE GeoSpring Hybrid Water Heater
Subcooler Unit
Monitor & Improve!!

14. Key Components Fujitsu 12RLS2 (1 ton) GE GeoSpring
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15. Important Features
Micro-Channel Coil
Centrifugal Duct Fan

16. Connect Liquid Refrigerant Line
Airstream Flows Over Coil
Saturated Liquid From Indoor Unit
Subcooled Liquid to Outdoor Unit

17. Centrifugal Fan
10” Square Duct
8” Round Duct
GE GeoSpring
Actuated Louvers

18. Solid Model

20. Combine Together Deliver Heated Airstream to GeoSpring Intake
Heated Airstream Will Diffuse Into Garage if GeoSpring is not Running

21. University Facilities Garage
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22. Estimated Cost (With Rebates)
Subcooler Unit
Fujitsu 12RLS2
GE GeoSpring
Installation
Total Capital Cost
= $ = $ = $ = $ = $

23. Payback Period How will The Subcooler Save Money?
By increasing the performance of the Heat Pump!
COP “With Subcooling” > COP “No Subcooling”

24. Payback Period
Equation derived with help from Peter Talmage.

25. Payback Period Price of Electricity=$0.16/kWh*
4817 Hours of Operation Per Year**
Sources: (* Bangor Hydro ** James LaBrecque)

26. Payback Period
Payback Period* = 24.4 Years

27. Motivation
Source: Google Patents

28. Motivation
THEIR TECHNOLOGY: ADDITIONAL CONDENSER, EXPANSION VALVE, EVAPORATOR, AND COMPRESSOR
OUR TECHNOLOGY: ONE ADDITIONAL COIL.

29. Summary Subcooler Unit Increases Heat Pump’s COP & EER
University of Maine Facilities Garage
Monitor Installation:
Fujitsu Mini-Split Heat Pump
Geospring Hybrid Water Heater
Subcooler Unit
Improve Design!

30. Final Marketable Product $$$
Mass Produce as an Accessory for Heat Pump
Minimal Installation Time for HVAC Technician
Customize Where Heated Airstream is Delivered
Free Heat Is Currently Being Wasted!!

31. Thank You For Your Time!