IDM ¦ Technology/IT
Range for use of cooler waste heat
Coefficient of performance -
m3 . Not only does the food production line draw cold from this,
but the CO2 heat pump also uses the buffer as a source of energy
to heat the cleaning water to 75 °C. In this way, it participates just
as much as the new chiller. In this way, it participates in the cold
production just like the new HTWP with its cold side. Its thermal
output is 160 kW.
Sintef recorded the performance data over a week. The combined
COP of propane and butane stages oscillated between 2.6
and 4.1 over the course of a week, with the aforementioned mean
value of 3.4. The pure temperature swing approached 108 K during
the observation period. For the time being, the refurbishment
did without heat recovery from the NH3 chiller. The recooler blows
its waste heat into the atmosphere. Sintef calculated the loss. According
to this, the coefficient of performance of the HTWP should
increase by a COP of about 0.5 to an average value of 3.8 to 4.
In the analysed period of one week, the process heat demand totalled
117 MWh, the hot water demand 11 MWh and the process
cooling demand 77 MWh.
Mainly standard components
Except for the compressor, the machine is based on standard
components. The heat pump experts succeeded in convincing the
compressor supplier Dorin to convert the 300 kW gross tank compressor
to the high temperature of 130 to 140 °C in the factory.
Dorin did not have to break any new ground, however. In a preliminary
test, the essential modifications had already been worked
out on a 20 kW compressor. The client was also SINTEF. Details can
be found in a publication by Schlemminger et. al. entitled "Design
and experimental results of a high-temperature propane-butane
heat pump". It is available on the
web. The modifications compared
to a standard compressor consist,
among other things, of an oil sump
heater that keeps the lubricating oil
permanently at 60 °C, so that sufficient
lubrication is ensured during
the periodic starts. Previously, Dorin
had to find a suitable lubricant
for the high-temperature application
in contact with hydrocarbons
(propane/butane) without ageing.
Christian Schlemminger's conclusion:
"The unit copes well with
the requirements. It has already run
for more than 2,500 hours and we
are confident that it will last another
ten years."
www.sintef.no
www.dkv.org www.tine.no
"The performance of the new HTHP results
in potential savings of 62 % in energy
consumption and up to 94 % in CO2 emissions
compared to a combination of refrigerationbased
ice water production and gas- or
oil-based hot water production. The study
successfully demonstrated that simultaneous
provision of process ice water and hot water
with a heat pump is technologically possible
and that retrofitting into an existing energy system can also be implemented in an
economically and ecologically sensible way." (Taken from: Schlemminger/Ahrens: Hightemperature
heat pumps with natural refrigerants).
Note: The energy and CO2 savings figures are based on the Norwegian energy mix with a
share of 95 % renewables, mainly hydropower, in electricity generation.
Regarding the economic efficiency, it should be said that in Norway, due to the lack of
a natural gas grid structure, the liquid energy source is just as expensive per 1 kWh as
electric power, namely currently about 10 cents/kWh. However, due to the liquid delivery
and the long transport routes, the prices differ considerably. Norwegian studies therefore
find it difficult to make a transferable economic calculation.
38 · May/June 2022 ¦ international-dairy.com
Figure 3:
Coefficient of performance
and Carnot
efficiency of the HTWP.
The blue dashed ellipse
defines the coefficient
of performance to be
expected when using
the waste heat from
the chiller. ws Heat
sink, wq Heat source
The results
Temperature lift -
Propane-Butane HTHP
/www.sintef.no
/www.dkv.org
/www.tine.no
/international-dairy.com
