RESULT 149
IEA
CA 90.075/2A.H05
OECD
energy efficiency
Refrigeration heat
recovery
Refrigeration heat
recovery system
Summary
The system was installed in a
poultry processing plant in
Brampton, Ontario, Canada,
owned by Maple Leaf Mills
Limited, with partial funding
from Energy, Mines and
Resources, and the Ontario
Ministry of Energy as a
grant for research and
development.
The system was designed to
recover low grade energy
normally exhausted by
refrigeration equipment, and
upgrade this recovered
waste heat using a heat
pump to supply process hot
water.
The project has
demonstrated the technical
and economic viability of
this system in a poultry
processing plant. However,
this system is not limited to
poultry plants, but can be
adapted for virtually all
plants that require both
refrigeration and hot water.
To date, the heat recovery
system has operated with an
average Coefficient of
Performance (COP) of
approximately 10.7. Under
these conditions, the system
can provide a simple
payback of approximately
2.9 years.
Highlights
• Payback period of
2.9 years
• Reduction in
refrigeration system
maintenance
• Improved
refrigeration system
efficiency
Cascading
condenser.
Centre for the Analysis and Dissemination of Demonstrated Energy Technologies
Aim of the Project
expansion of the heat pump
refrigerant (R12) at the same
time condensing the ammonia
refrigerant for the plant’s
refrigeration system (ice
machine). The use of this
cascading system eliminates
the need for an intermediate
glycol runaround loop heat
exchanger, reducing the
investment cost of the system.
The purpose of this project is to
demonstrate the technical and
economic feasibility of a heat
recovery system to recover
waste heat from the hot
ammonia gas exiting the
refrigeration equipment, and to
use this to produce hot water
for the process using a
cascading heat pump.
Figure 1 shows a schematic of
the heat recovery system
installed at the company. The
Existing refrigeration
equipment
177 kW
cooling
capacity
Existing
ice machine
(Ammonia)
NH3
111 kW
cooling
capacity
Heat pump evaporator
(cascading condenser)
Shell & tube
Preheater
system
1st stage
of heat
recovery
Glycol &
water loop
Glycol
circulating
pump
Glycol
fill pump
R12
Exp.
valve
Condenser
Plate heat
exchanger
Heat
pump
system
2nd stage
of heat
recovery
3.5 l/s
11.8°C
Cold water
supply
177 kW
24.8°C
The first stage of heat recovery
is a preheater system. This
involves heat exchange
between the ammonia
refrigerant from the
refrigeration equipment and a
30% solution of glycol and
water in the glycol circulating
The Principle
The innovative feature of this
system is the use of a cascading
condenser. This is a heat
exchanger which allows direct
(Ammonia)
NH3
heat recovery system is
connected to approximately
460 kW of refrigeration
capacity. The energy, which is
normally exhausted to the
atmosphere by the evaporative
condensers, is recovered in two
stages.
Max. 63°C
avg. 40.6°C
149 kW
6.8 l/s
Water circulating pump
Average
system
energy
usage
27 kW
22,750 litre
storage tank
40.6-63°C
Existing
storage
tank
To process
40.6-63°C
Figure 1:
Schematic
representation of the
heat recovery
system.
loop. This heat exchange
occurs inside the shell and tube
heat exchanger. The heat
absorbed in the glycol
circulating loop is transferred
by a plate heat exchanger to the
cold water supply. The glycol
runaround system, that is the
plate exchanger and the shell
and tube heat exchanger, is
necessary to ensure that the
supply water does not come
into direct contact with the
ammonia refrigerant. The plate
heat exchanger is designed to
heat the incoming water by
11°C at a flow of 7.6 l/s. At
lower flow rates, the cold water
will be heated to higher
temperature, if the refrigeration
load is available.
The second and principal stage
of the heat recovery occurs in
the cascading condenser of the
heat pump. The cascading
condenser is a heat exchanger
which allows the ammonia
refrigerant to condense thereby
giving up its latent heat to the
heat pump refrigerant (R12)
which simultaneously
evaporates. The heat pump
refrigerant leaves the cascading
condenser as a low pressure,
low temperature gas and
returns to the compressor.
Here, its temperature is raised
yet again before it is passed on
to a condenser where its heat is
transferred to the process
water. The water is pumped
into a 22,750 litre pressurized
thermal storage tank which is
connected to the plant’s
existing water heating system.
The Situation
The basic concept has been
successfully tested at a Maple
Leaf Mills plant in Petersburg,
Ontario, Canada, as part of a
research project funded by the
Canadian Electrical Association and Ontario Hydro. The
system installed in Brampton is
a packaged heat pump heat
recovery system developed by
BEST Energy Systems Inc.
with the cooperation of Dryline
System especially for the
Petersburg project.
There were no major changes
to the original design other than
the relocation of some
equipment in the plant. The
data representing the system
performance for two summer
months in 1987 is given below.
• The hot water flow rate
averages approximately 3.84.6 l/s with peaks of about
6.8-7.6 l/s.
system, thus recovering more
energy at minimum of cost.
The installation of the heat
pump has increased the
capacity of the ice machine.
Theoretically, it is estimated to
be in the range of 1-2%,
although this cannot be backed
up by measured data. The
increased capacity was the
result of reducing the head
pressure of the existing
refrigeration system and thus
providing a slightly higher load
to the heat pump. The
refrigeration heat recovery
system has other benefits such
as the elimination of the
evaporative condenser system
and a reduction in the
refrigeration system
maintenance.
• The plate heat exchanger
increases the cold water
supply temperature by
approximately 13°C. This
represents an average of
177 kW with peaks of
approximately 409 Kw.
Economics
• The heat pump increases the
temperature of the water by
approximately 8°C resulting
in an average heating
capacity of 149 Kw with
peaks of 300 Kw.
The investment for this project
is CAD 165,000, including
engineering (CAD 24,000),
equipment; heat pump, storage
tank, plate heat exchanger,
pumps, cascading condenser,
shell and tube condenser (total
cost: CAD 104,000) and
installation (CAD 37,000).
• The average energy input
into the heat recovery
system is 27 kW. The peak
energy input is 51 kW.
• The average daily thermal
energy delivered by the heat
recovery system is 7030 kW
per day or 293 kW per hour.
The heat pump has a greater
cooling capacity than is
currently required. This gives
the opportunity for additional
refrigeration equipment to be
added to the existing heat pump
The preliminary results of this
demonstration project illustrate
both the technical and
economic viability of this type
of heat recovery system.
The energy saving, assuming
75% boiler efficiency, is
330 m3 of natural gas annually
corresponding to CAD 60,550.
The new system eliminated the
need for the older evaporative
condensers, as a result the
water demand is reduced by 6.8
million litres for an extra
CAD 2,490 saving. Moreover,
58,125 kWh/year (the
electricity used to operate the
older system) is recovered,
corresponding to an additional
cost saving of CAD 2,325
(assuming CAD 0.04/kWh).
The operating cost of the
system (27 kW x 24h x
365 days x CAD 0.04)
represents a supplementary cost
of CAD 9,495. The net cost
saving is approximately
CAD 56,000 giving a simple
payback of 2.9 years. This
calculation does not include
cost savings from improved
performance of refrigeration
equipment and the elimination
of the maintenance cost of
evaporative condensers.
Host Organisation
More Information
Tend-R-Fresh
32 Kennedy Rd. South
L6W 3E3 Brampton
Ontario
Canada
Tel.: +1-416-453-6260
Contact: Mr J. Pimentel
Dryline System
2359 Royal Windsor Drive
Unit 6
L5G 4S9 Mississauga
Ontario
Canada
Tel.: +1-416-855-2331
Contact: Mr E. Pasquini
Engineering
Organisation
Best Energy Systems Inc.
208 Wyecroft Rd.
L6K 3T8 Oakville
Ontario
Canada
Tel.: +1-416-849-6522
Contact: Mr P. Rowles
Please write to the address below if you require more information.
IEA *
OECD
energy efficiency
Swentiboldstraat 21,
6137 AE Sittard,
P.O. Box 17, 6130 AA Sittard,
The Netherlands,
Telephone: +31-(0)46-595-224,
Telefax: +31-(0)46-510-389.
* IEA:
OECD:
IEA
The Scheme
The IEA was established in 1974 within the
framework of the OECD to implement an
International Energy Programme. A basic
aim of the IEA is to foster co-operation
among the 22 IEA Participating Countries to
increase energy security through energy
conservation, development of alternative
energy sources, new energy technology, and
research and development (R&D).
CADDET functions as the IEA Centre for
Analysis and Dissemination Demonstrated
Energy Technologies for all IEA CADDET
member countries.
This is achieved, in part, through a
programme of energy technology and R&D
collaboration currently within the framework
of 35 Implementing Agreements, containing
a total of more than 60 separate collaboration
projects.
Demonstrations are a vital link between
R&D or pilot studies and the end-use market.
Projects are published as a CADDET
‘Demo’ or ‘Result’ respectively, for ongoing and finalised projects.
This project can now be repeated in
CADDET member countries. Parties
interested in adopting this process can
contact their National Team or CADDET.
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June 1993