Waste-Heat Recovery
Saving the environment and saving money can be as easy
as re-using hot exhaust air. That means you’re on the
front line for energy-savings opportunities. Team up with
co-workers to spot ways to recover waste heat – it’s good
for the environment and good for your bottom line.
3. Retrofits
Uncover energy savings
Check out your waste-heat recovery. Proper maintenance
will save energy by capturing and re-using rejected heat,
instead of buying more energy. To conserve energy and
cut costs, consider three main areas:
1. Housekeeping
› Identify sources of waste heat.
› Eliminate as many sources of waste heat as possible.
› Reduce the temperature of the remaining waste heat.
› Inspect and maintain equipment to minimize the
production of waste heat.
2. Low-cost opportunities
› Capture waste heat from a clean waste stream that
normally goes into the atmosphere or down the drain,
and then pipe the waste stream to where it can be used.
› Use waste-process water as a heat source for a
heat pump.
› Use the heat of the plant effluent being treated in a
wastewater treatment plant as a heat source for a
heat pump.
› Re-use hot exhaust air for drying.
› Install automatic controls.
› Re-use heat from cooling hydraulic oil (e.g. within
moulding machines and the injection moulds
themselves). This also reduces the electrical load on
the production process.
Install waste-heat reclamation equipment (e.g. replace
a cooling tower circulation loop with a shell-and-tube
heat exchanger).
Upgrade or replace outdated waste-heat reclamation
Combine a flue gas heat recuperator with a heat pump.
Use an absorption heat transformer, which reclaims
waste heat by using a solution of lithium bromide.
Use a low-grade chiller, which can convert low-grade
heat to spare cooling.
Integrate a compact heat exchanger with other
In a large computer centre, capture generated heat by
using thermal storage.
Recover heat generated through refrigeration and
upgrade the heat by using a heat pump.
Consider converting high-temperature flue gas heat
(e.g. from metallurgical furnaces) into superheated
steam for electric power generation.
Evaluate the potential for your waste-heat
1. Is your furnace or boiler fitted with an economizer or
air heater to capture waste heat from the flue gases?
Recycled paper © Her Majesty the Queen in Right of Canada, 2009
Cat. No. M4-76/3-2009E (Print)
ISBN 978-1-100-11656-3
Cat. No. M4-76/3-2009E-PDF (On-line)
ISBN 978-1-100-11657-0
❏ YesAt the next shutdown, make sure the unit is
operating efficiently; check fins and tubes for
damage, especially from corrosion; and remove
accumulated soot.
5. Is any process water warmer than 38°C when it
leaves your facility?
❏ YesInstall a heat exchanger to recover heat for use
in process or space heating.
❏ NoIf the wastewater flow is large enough, a heat
pump or an absorption heat transformer may be
a good idea – consult an engineer.
Done by: ______________________________________
❏ NoInstall heat-recovery equipment or an economizer.
Date: _________________________________________
Done by: ______________________________________
6. Is any cooling process water dumped down the drain?
Date: _________________________________________
❏ YesUse the warm water directly in another process.
Or use a heat exchanger to recover heat for
another process.
2. D
oes your heating, ventilation and air-conditioning
(HVAC) system exhaust a lot of air at room
temperature or higher?
❏ YesInstall a heat-recovery system to preheat and
pre-cool make-up air.
❏ No
No action required.
Done by: ______________________________________
Date: _________________________________________
3. C
an a ground-source heat pump be used to condense
refrigerant, instead of using cooling-tower water?
❏ YesHire an engineering consultant to evaluate the
use of a ground-source heat pump.
❏ No
No action required.
Done by: ______________________________________
Date: _________________________________________
❏ NoIf cooling water is sent to a cooling tower, replace
the cooling tower with a heat exchanger to
recover heat from the water for other processes.
Done by: ______________________________________
Date: _________________________________________
7. D
oes any equipment exhaust a large amount of water
❏ YesUse either mechanical or thermal vapour
compression to upgrade the exhaust vapour into
a more useful energy source.
❏ No
No action required.
Done by: ______________________________________
Date: _________________________________________
4. C
an exhaust fan air be ducted directly into another
area for space heating?
❏ YesInstall ducts and a blower to move air into the
area to be heated.
❏ NoPreheat make-up air or recover heat with an
air-to-air heat exchanger.
Done by: ______________________________________
Date: _________________________________________
Aussi disponible en français sous le titre : Ensemble, économisons
l’énergie! La récupération de la chaleur perdue
For more information: oee.nrcan.gc.ca/industrial
Natural Resources Canada’s Office of Energy Efficiency
Leading Canadians to Energy Efficiency at Home, at Work and on the Road
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