Air Conditioning and Refrigeration Center. College of Engineering. University of Illinois at Urbana-Champaign.
Abstract
Electrochemical processes can be combined into thermodynamic cycles that can produce refrigeration
effects. The technical feasibility and design parameters of electrochemical refrigeration systems were studied.
Modeling of thermodynamic, kinetic, and transport processes have been undertaken.
The systems under investigation are divided into two groups: direct methods and indirect methods. Direct
methods utilize the heat absorption and rejection associated with the entropy change of reaction that occurs as part
of an electrically-driven chemical reaction. Indirect methods use some other aspect of an electrochemical reaction
such as pressure production to drive a cooling system.
Thermodynamic equilibrium analyses of direct methods have been performed including development of a
proof of Carnot limitations. A variety of potential chemical reaction systems have been investigated with respect to
feasibility for laboratory prototype systems and future applications. The properties of an ideal reaction system are
discussed and several possible reaction types are suggested for investigation.
The continuous flow direct method consists of two electrochemical cells operating in reverse of each other
with reactants pumped between them via a regenerative heat exchanger. More detailed analyses including
irreversibilities have shown technical feasibility. These analyses included ohmic resistance, limitations due to the
reaction rate kinetics, mass transport losses, and losses due to the internal regenerative heat exchange process. This
model identifies some of the tradeoffs in design and places upper and lower bounds on design parameters such as
surface heat flux and COP. The model calculation is based on published measurements of reaction data. The
system is very sensitive to losses in the cells because the electricity cycled internally is much larger than the heat
transferred externally.
Small scale laboratory tests have demonstrated cooling using a D-sized NiCd battery and a cell generating
gaseous chlorine and hydrogen from hydrochloric acid.
A number of indirect methods for refrigeration are reviewed.Air Conditioning and Refrigeration Project 12
