Kelvion Heat Exchange Solutions
RETHINK
THERMAL EFFICIENCY
RETHINK SOLUTIONS
Varying extreme conditions require different solutions, from cold to very hot climates, all over the world. Factors such as the maximum temperature required for the given process, and the availability of water will influence which free cooling system to choose. Typical heat rejection systems include dry coolers, adiabatic coolers, hybrid coolers and cooling towers.
Effective ambient temperature
The performance of a heat exchanger is proportional to the temperature difference between the process medium and the heat transfer medium flowing through it.
OPTIMIZING FREE COOLING POTENTIAL AND IMPROVING EFFICIENCY BY REUSING WASTE HEAT
There is no one fits all solution. In this paper we’ll have a closer look on the different technologies, climate trends and heat recovery cases to encourage you to rethink thermal efficiency
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DRY COOLER
The performance of this technology is highly dependent on the difference in temperature between the process water mixture and the ambient air flowing through the exchanger.
Dry coolers transfer energy by heating the ambient air and thus they require a large air flow volume.
This means that a dry cooler’s performance is directly governed by the dry bulb temperature of the atmosphere.
Ambient Temperature
Water Availability
Energy Consumption
Water Consumption
ADIABATIC SYSTEM
One way of optimising a dry cooler is to use an adiabatic cooler with a spray or pad system. The adiabatic system reduces the temperature of the air within the exchanger by evaporating water into the ambient air to increase its humidity.
This is effective due to the fact that, as you increase the humidity, you also reduce its dry bulb temperature.
Adiabatic dry coolers are able to offset high ambient temperatures throughout the year, increasing the free cooling potential of a site.
ADIABATIC
SPRAY SYSTEM
Ambient Temperature
Water Availability
Energy Consumption
Water Consumption
ADIABATIC
PAD SYSTEM
Ambient Temperature
Water Availability
Energy Consumption
Water Consumption
HYBRID COOLER
Another solution to enhance your free cooling potential in very hot regions is a hybrid system.
The hybrid cooler offers 2 different cooling modes. A dry mode where heat is exchanged with ambient air via its sensible enthalpy. In wet mode the system is watering the coil and uses the water sensible enthalpy as well as its latent enthalpy, via an adiabatic effect where air is evaporating the water.
This allows the system to work with ambient dry bulb temperature well above process fluid outlet temperature.
Ambient Temperature
Water Availability
Energy Consumption
Water Consumption
CLIMATE IS KEY
Ambient temperature is not the only metric to be considered. The effficiency of heat exchanger is also highly influenced by the difference between process temperature out and ambient temperature.
Assuming the below temperatures and a process temperature of 35°C we can see the following:
COLD CLIMATE
You will have a difference of 35°-25° = 10K
As the temperature difference between process temperature and ambient temperature is high enough, a dry cooler could be the right choice here. In case of extreme low ambient conditions measures like shutters could maintain uptime operation
HOT CLIMATE
You will have a difference of 35°-33° = 2K
This difference is too low to allow efficient heat rejection. Adiabatic systems can reduce the air inlet temperature up to 8-10 K
VERY HOT CLIMATE
You will have a difference of 35°-38° = -3K
The difference is negative and needs to be increased with an appropriate system like an hybrid cooler.
You could achieve the requested capacity even with an ambient temperature higher then you process out temperature because you are using wet cooling.
This can reduce the air inlet temperature up to 12 K
This is something that Dry Coolers could never achieve in any case, and that adiabatic would struggle to do and could even be impossible to achieve (because no wet cooling, and no 100% humidification of air).
A Cooling Tower could manage these high ambient temperatures as well but at the expense of higher water consumption and higher normative requirements.
EXPLORE SOME CLIMATE CASES
FRANKFURT
To achieve a capacity of 2000 kW:
[based on water in: 40°C / water out: 35°]
-
In this region, a Dry Cooler will need assistance only 5% of the time.
-
A Hybrid Cooler could meet the required capacity the whole year long while taking 50% less footprint than an Adiabatic Pad system and significantly less water than a cooling tower.
Annual Temperature Distribution
4-15°C
39°C
-9°C
Mean Temperature
Relative
Humidity
Majority
Hours
Maximum Temperature
Minimum Temperature
Temperature [°C]
Hours per year
Free Cooling
Footprint
Electric Consumption
Water Consumption
DRY COOLER
100%
95%
-
ADIABATIC
112%
100%
HYBRID
72%
100%
COOLING TOWER
49%
100%
Initial Unit Cost
BEIJING
To achieve a capacity of 2000 kW:
[based on water in: 40°C / water out: 35°]
-
In this region, a Dry Cooler is not appropriated, and only adiabatic or wet cooling solutions are suitable.
-
A Hybrid Cooler take less footprint than the 2 other Adiabatic solutions while being effective 100% time of the year.
Annual Temperature Distribution
-2-28°C
40°C
-14°C
Mean Temperature
Relative
Humidity
Majority
Hours
Maximum Temperature
Minimum Temperature
Temperature [°C]
Hours per year
Free Cooling
Footprint
Electric Consumption
Water Consumption
DRY COOLER
100%
97%
-
ADIABATIC
112%
99%
HYBRID
39%
100%
COOLING TOWER
18%
100%
Initial Unit Cost
HOUSTON
To achieve a capacity of 2000 kW:
[based on water in: 40°C / water out: 35°]
-
Due to high ambient, Dry Coolers could only meet the demand w/o assistance 61% of the year.
-
While a Hybrid Cooler could achieve the capacity the whole year long while consuming less electrical power and footprint compared to an Adiabatic Pad system and significantly less water than a Cooling Tower.
Annual Temperature Distribution
19-29°C
41°C
-2°C
Mean Temperature
Relative
Humidity
Majority
Hours
Maximum Temperature
Minimum Temperature
Temperature [°C]
Hours per year
Free Cooling
Footprint
Electric Consumption
Water Consumption
DRY COOLER
100%
61%
-
ADIABATIC
112%
91%
HYBRID
72%
100%
COOLING TOWER
37%
100%
Initial Unit Cost
DUBAI
To achieve a capacity of 2000 kW:
[based on water in: 40°C / water out: 35°]
-
In this region, a Dry Cooler is not appropriated, and only adiabatic or wet cooling solutions are suitable.
-
2 Adiabatic Pad systems are required whereas only 1 Hybrid Cooler is needed with less water consumption than a cooling tower, which is also crucial in this area.
Annual Temperature Distribution
21-33°C
46°C
11°C
Mean Temperature
Relative
Humidity
Majority
Hours
Maximum Temperature
Temperature [°C]
Hours per year
Minimum Temperature
Free Cooling
Footprint
Electric Consumption
Water Consumption
DRY COOLER
-
-
-
-
ADIABATIC
100%
97%
HYBRID
48%
100%
COOLING TOWER
22%
100%
Initial Unit Cost
-