Fan power and fan heat gain/generation

In summary, the conversation discusses the topic of fan power and heat generation and questions whether all fan power is converted to heat. The engineer is trying to determine the amount of heat gain from the fan to the air and considers the conversion of electric energy to kinetic energy and friction loss. The conversation also touches on the concept of air heat gain and what happens to the kinetic energy of the fan when it is turned off.
  • #1
momomomoses
3
0
fellow engineers,

hi I'm totally new here so hello everyone.

I'm a mechanical HVAC design engineer and I have a question about fan power and fan heat gain/generation. My main concern is the temperature rise in the air passing through the fan.

I've been researching in books and on the internet but haven't got any concrete result.

I'm trying to think in terms of energy. It all started with electric energy to the fan, then it is converted to the following
1) kinetic energy of the fan
2) kinetic energy of air, which causes an increase in air temperature
3) friction loss of the fan system, which is released as heat i.e. the kinetic energy or air which causes an increase in air temperature.

however at this website "www.engineeringtoolbox.com/electrical-motors-heat-gain-d_707.html"[/URL] it states that ALL fan power is converted to heat to its surrounding. I've also confirmed something like this with a Carrier engineer.

Is is possible? I always think of "air heat gain" as an increase in air motion. Am I missing something important here?

Thanks
 
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  • #2
Fans have been known to stir up air. Some of the energy from the fan motor will cause the fan blades to turn, causing the air to move.
 
  • #3
thanks for you reply.

that's my point exactly. only some of the fan motor energy out work to the air, so only part of the fan energy is "heating up" the air, right? so how would you determine the amount of heat gain from the fan by the air?
 
  • #4
When you turn off the fan, does the air continue to move? Where did the kinetic energy go?
 
  • #5
thanks for your reply.

after the fan is off the air keeps moving slower and slower because of friction, releasing the "heat" to the surrounding.

So are you suggesting that the electric energy is converted to
(1.1) kinetic energy of the fan
(1.2) friction loss of the fan, which is released as heat and increases the air temperature

and then the kinetic energy of the fan (1.1) is converted to
(2.1) kinetic energy of air, which causes an increase in air temperature

therefore the entire heat given out from the fan is (1.2) and (2.1), which is the electric energy input?
 

1. How does fan speed affect heat generation?

As fan speed increases, the fan will generate more heat. This is because the motor that powers the fan will need to work harder and use more energy to rotate the blades at a faster speed. This increase in energy usage results in an increase in heat generated by the fan.

2. Can the heat generated by a fan impact the surrounding environment?

Yes, the heat generated by a fan can impact the surrounding environment. This is especially true for large and powerful fans, which can generate a significant amount of heat. If placed in a small and poorly ventilated room, the heat generated by the fan may contribute to an increase in the overall temperature of the room.

3. How can the heat generated by a fan be managed?

The heat generated by a fan can be managed in several ways. One way is to choose a fan with a lower speed setting, which will generate less heat. Another way is to ensure proper ventilation in the room where the fan is being used. This can help dissipate any heat generated by the fan. Additionally, using an energy-efficient fan can also help reduce the amount of heat generated.

4. Is there a difference in heat generation between different types of fans?

Yes, there can be a difference in heat generation between different types of fans. For example, a traditional ceiling fan will likely generate less heat compared to a high-powered industrial fan. Additionally, the design and motor of a fan can also impact the amount of heat generated.

5. Can the heat generated by a fan affect its performance?

Yes, the heat generated by a fan can affect its performance. If a fan becomes too hot, it may start to malfunction or even shut down. This is why it's important to properly manage the heat generated by a fan and ensure it has proper ventilation to prevent overheating.

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