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

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

Department of Mechanical EngineeringOregon State University

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

Basic Expander/Compressor Cycle

Power Cycle

Vapor Compression

Cycle

CondenserCooling

Components QLQou

t

PowerGenerating

ComponentsQH

Work

MotiveFluid

CoolingFluid

Fluid Fluid

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

How it Works - Heat Exchangers

Why?• Large surface area

• Laminar flow

• Change in relative importance of phenomenaand enables systems integration

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

•

•

•

Results in smaller, cheaper, better

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

Completed Work – Breadboard Setup

Evaporator

Flow Meters

VaporizerPump

Dyno

Expander/ Compressor

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 rpm—adequate 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.

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.

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.

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.