Let Your Generator Set Breathe with a Remote Cooling System
on 05-19-201409:36 AM - last edited on 06-05-201411:52 AM by cboysen
Most standby diesel and gas generator sets are equipped with radiators to regulate temperature. However, there are times when it is better to use a remote cooling system for temperature control. In urban installations where the generator set is in a basement or on the ground floor of a building, it is often impractical to use a large air inlet on one side of the building and a large air exhaust on the other side. Implementing a remote radiator behind the building can be a much better option, because all the cooling noise is on one side of the building and most of the mechanical noise from the engine can be contained inside the power room.
Just because there is no radiator in the power room, it doesn’t mean that the room can be completely sealed. Not only does the engine need combustion air, but both the engine and the generator need a constant source of cool air to keep from overheating. Approximately seven percent of the heat from the fuel burned in a generator set is radiated into the power room by either the engine or the generator. For example, a generator set producing 2MW will give off almost 148 kW (50,000 BTUs) of heat in the power room. Unless there is constant airflow through the room, the temperature will keep getting hotter. Under these conditions, the insulation on the generator windings, the torsional damper on the front of the engine, and the electronic components will eventually begin to fail.
The damper at the front of the engine and the generator insulation are the two components most at risk from overheating. The damper requires moving air at temperatures below 50 °C (122 °F), and the generator’s entry air needs to be as far below 40 °C (104 °F) as possible. This can be best achieved by either routing the inlet air so it enters the room low to the ground by the back of the generator, or by installing a forced air duct system, or air curtain, to push cool air out of floor vents around the generator set with a room exhaust opening above the generator set. Both of these strategies optimize cool airflow.
Routing the air close to the ground is easier to do, but close attention to the airflow around the damper is required to make sure a recirculating vortex doesn’t trap hot air. Creating an air curtain has the added benefit of collecting the heat in a column above the generator set, keeping the rest of the room cooler. Other combinations of air inlet and outlet locations do not provide enough cool air near the damper and generator, so they require additional airflow strategies to keep the room cool.
Designing power rooms for optimized airflow requires a bit of planning. We recommend using the equation below to figure out exactly how much airflow is needed to keep a steady temperature:
Q = needed airflow in cubic meters per minute
H = the heat being put into the room in kW
D = the density of air (about 1.099 kg per cubic meter)
Cp = the specific heat of air (about 0.017 kW minute per kg per degree in Celsius)
dT = the amount of heat that can go above the outside ambient temperature in Celsius
Let’s run through it together. If the outside air temperature stays below 30 °C, (86 °F) and you want to keep the room air temperature below 40 °C (104 °F), then the dT equals 10 °C (18°F). Now, let’s apply that to a two-megawatt engine that radiates 147 kW of power into the room:
Q=786.8 cubic meters per minute (27,786 cubic feet per minute)
Note: The final number only represents the value needed to cool the generator set. If the engine does not have outdoor ducting connected its air filters, then the amount of air used for combustion needs to be added to get the total amount of air that needs to enter the room.
For more information on how to design an optimized power room and get the most from your generator set, please contact your local Cat® dealer. You can also download our Application and Installation Guide for Engine Room Ventilation here.
We’d like to hear more about your experiences with power room setup and generator set airflow optimization.
How would you solve airflow issues in urban settings?
What does this equation tell you about your own power room setup?
What can Caterpillar do to help you get more from your generator set?