Overview of Heat Activated Heat Pump Development Using the E/C Cycle

1
Overview of Heat Activated Heat Pump Development
Using the E/C Cycle
Department of Mechanical Engineering Oregon State
University

• Richard B. Peterson, Tom Herron, Hailei Wang, and
  Kevin Drost

2
Motivation and Opportunities

• Motivation
• Waste heat, or low-grade heat, is often a free
  resource.
• Many applications for cooling involve engines
  with a hot exhaust stream.
• Burning fuel releases 10x to 100x the energy
  contained in batteries.
• Current technology (microchannel heat exchangers
  and inexpensive expander/compressor machinery) is
  poised for commercial viability.
• Opportunities (not an exhaustive list!)
• Tactical cooling systems for the military use
  (current funder)
• Automotive air-conditioning in current and new
  technology vehicles (hybrids). Also RVs, Trucks,
  Planes, etc.
• Chem and bio protection suit cooling for first
  responders
• Combined heat, cooling, and power systems for
  residential service
• Auxiliary power unit (diesel, micro turbine,
  etc.) add-ons where cooling is needed

3
Basic Expander/Compressor Cycle
Work
Fluid
Fluid
Power Generating Components
Cooling Components
Condenser
Qout
QL
QH
Motive Fluid
Cooling Fluid
Vapor Compression Cycle
Power Cycle
4
Key Technologies MECS
MECS Microtechnology-based Energy and Chemical
Systems

• MECS relies on
• High rates of heat and mass transfer afforded by
  microchannels
• Extremely high degree of control of processes

• To miniaturize a wide range of systems
• Chemical (reactors, mixers, separators, etc.)
• Energy (heat transfer devices, combustors, etc.)
• Biological (biosensors, bioreactors, etc.)

• Enabling portable and distributed systems

5
How it Works - Heat Exchangers
Why?


Large surface area


Laminar flow


Change in relative importance of phenomena and
enables systems integration

• e.g. boiling (surface tension)
• better thermal management

Results in smaller, cheaper, better
6
Considerations

• Use Commercially Available Components Where
  Possible
• Military Systems
• Cost is not much of a consideration
• Reliability, size, and weight are critical
• Non-portable Commercial Systems
• Cost is a driver
• Reliability is important
• Size and weight not critical
• Portable (automotive?) Commercial Systems
• Size, reliability, and cost are critical
• Weight important, how much is driven by specifics

7
Completed Work Breadboard Setup
Pump
Vaporizer
Flow Meters
Dyno
Evaporator
Expander/ Compressor
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Summary of Breadboard Work

• We have demonstrated a prototype
  expander/compressor operating at 150 W of cooling
• Mean device efficiency was shown to be 65-70 at
  1500 rpmadequate to reach a COP of 0.7 at design
  conditions.
• No regenerator was used in the breadboard system.
• Follow-on work will include
• Investigate the thermodynamic effects of a
  regenerator in the power cycle.
• Build and test a 2 kW split cycle heat activated
  cooler.
• Build and test a 5 kW combined cycle cooler.

9
Completed Work 2 kW System

• Split Cycle E/C System
• Separate power and vapor cooling cycles
• Oil loop used for the power cycle for lubricating
  the expander
• Built from both commercial and semi-custom
  components
• Status
• System has been assembled
• Testing of the individual components and overall
  system complete
• Performance data shows expander component
  requires higher efficiency.

10
Summary

• We have demonstrated working systems with
  promising performance.
• Key technology remains in the development phase
  an expander with the requisite efficiency.
• No regenerator has been used so far in our
  efforts.
• Microchannel component demonstration will be
  shown on the next generation system.

11
Next Step 5 kW System

• 5 - kW system development is underway with
  modeling studies and expander development.
• System will have a single fluid and a common
  condenser.
• Microchannel heat transfer components will be
  included in the overall system.
• Size, weight, and performance will be key issues
  to concentrate on.