# Tag Info

## Hot answers tagged hvac

27 votes

### Why does moving air feel cold?

There are a couple reasons. First of all, it's important to note that the sensation of warmth or coolness is only indirectly related to temperature. The receptors in your skin that deal with ...
• 3,211
15 votes
Accepted

### What is the most efficient means of warming a building with a high ceiling?

Your question sort of has two parts: How to supply heat, and how to keep it in. Large open rooms with a high ceilings are most efficiently warmed with radiant ceiling heat. Warm air rises, which ...
• 1,785
8 votes

### What is the most efficient means of warming a building with a high ceiling?

Another option to the radiant solution above would be under floor air distribution systems (UFAD) using displacement ventilation. These systems require a raised floor plenum which works well in ...
• 377
8 votes

### Converting air flow rate between kg/s and m^3/s

You need to consider the density of the air, which varies with temperature and air pressure. At 15 degrees Celsius, at sea level, the density of air is 1.225 ${kg}/{m^3}$. The table here gives air ...
• 9,447
7 votes

### How can I turn home gas (LPG) from liquid to gas?

Lighters usually use Butane. Gas bottles use some or all Propane. Propane pressures are MUCH higher. A plastic 'tank' filled with Propane would probably explode. As size increases the container ...
• 3,824
7 votes
Accepted

### Dead Load / Self Weight for ceilings & HVAC

I don't think what you are looking for really exists, in terms of a standardized list of HVAC/services loadings. Building codes don't usually specify dead loads, probably because they are, in ...
• 2,631
7 votes
Accepted

### Why is it more common to use ceiling fans instead of air pumps?

Mainly cost difference. And also, a fan is sufficient for the job. The problem being solved is thermal stratification. That's caused by a lack of vertical mixing; the warm air rises to the top, the ...
• 3,701
6 votes

### Convective fix for air conditioning dilemma?

Those two holes by themselves will have little effect. The pressure difference between the two ends of the holes will be so small that only a little air will flow. If you want to go thru all this ...
• 11.2k
6 votes

### Why do boiler exhaust stacks use tapered transitions?

The taper in the stack performs two functions: A tapered section is a lot more structurally resistant to wind loads This seems counter intuitive at first - after all, a tapered cantilever beam ...
• 5,303
6 votes
Accepted

### How does an expansion tank work?

It is better to think of it in terms of volume than pressure. The key point is that air is compressible while water is not. If you heat water is has to expand. If it is in a closed container then it ...
• 15k
5 votes

### Effective R-value of radiant barriers

Insulating against thermal conduction can be represented as an R-value because it is a linear calculation. I can add two or more R-values together and I will see a linear benefit. Insulating against ...
• 7,469
5 votes
Accepted

### How to minimize heat loss in an air extractor?

What you want is called a heat exchanger. Imagine two long air tubes with a thin wall between them. The air exiting the house travels in one tube, and entering air in the other, but in opposite ...
• 11.2k
5 votes

### How does one create a draft in a room (with a single window)?

The fundamental problem is that hot air must leave the room and cold air must enter it, both at the same time through the same single opening. The conflicting forces will mostly cancel each other out,...
5 votes

### Converting air flow rate between kg/s and m^3/s

HVAC-Systems usually give a Volume-Flow-Rate, hence $m^3/s$. If you need Mass-Flow-Rate ($kg/s$) you simply need to multiply with the density ($\rho$) of the fluid. The density can be calculated using ...
• 1,202
5 votes

### Why does moving air feel cold?

The air feeling cold is really your skin being cooled by forced convection and evaporation of sweat. With no air movement a boundary layer of hotter air forms over the skin and so because of the ...
• 151
5 votes
Accepted

### Humidity in home is much higher than outside

Sounds like you have covered your bases. The only thing I can recommend is gathering data and considering some scenerios to evaluate that data against. I am not an HVAC guy but can give you the 1000ft ...
• 7,469
5 votes

### Does venturi effect helps in reducing temperature of a room?

I don't think it will drop the temperature at all. What it might accomplish is increase the velocity of the air in the room. That will in turn affect the convective coefficient The convective heat ...
• 22.6k
4 votes
Accepted

### Where to insulate Underfloor air distribution system in a temperate climate

It depends — can you run air through the plenum without simultaneously running the active heating/cooling system? If not, you'll never get the benefit of its thermal storage capacity. For ...
• 6,749
4 votes

### What is the most efficient means of warming a building with a high ceiling?

Here are some ways to keep the warm air from escaping: Revolving doors prevent a constant stream of air exchange between the inside and outside. Air lock areas - a double-set of sliding doors can ...
• 5,930
4 votes
Accepted

### Calculating kWh for different timestep

I think you are getting power and energy confused, so I'll quickly define them before giving an answer. Energy energy is a measure of how much potential for work exists. If you had a battery, it ...
• 1,167
4 votes

### A humidifier before a heater and after a heater

warm air can hold more moisture than cold air so the amount of water you can suspend in the air will change depending on where you install the humidifier. Mounting the humidifier before the heater ...
• 4,618
4 votes

### Can Peltier Modules be practically used to cool a room?

Peltier thermoelectric cooling modules can be used to cool anything you like. It will not be economical compared to a standard off the shelf air-conditioner (R-134A compressor cycle). If you source ...
• 7,469
4 votes

### Practicality of energy recovery from HVAC systems?

So, if I understand correctly you are proposing to use a turbine in the exhaust vents in order to reclaim the energy from the flowing air. However, in most cases the air is flowing due to forced flow, ...
• 22.6k
4 votes
Accepted

### Identify this textbook

Thermal Environmental Engineering 3rd Edition by Kuehn, Ramsey & Threlkeld (1998), Pearson.
• 2,302
3 votes
Accepted

### How do dry storage cabinets work?

Not to jump the gun from @hazzey, but one of the product description images describes how the cabinet works: The English in the images is a little lacking (probably a translation from a Chinese ...
• 3,587
3 votes
Accepted

### Perfectly aerodynamic kitchen range hood

Making a duct that flares along an exponential curve to 2 feet (60cm) in diameter would create a larger duct that won't solve your problem. It would be an expensive duct to make (think tuba bell), ...
• 3,525
3 votes

### How to calculate indoor temperature?

The indoor temperature in the unheated case will be just the low pass filtered outdoor temperature. In steady state, therefore, the indoor temperature will be the same as the outdoor - at first ...
• 11.2k
3 votes
Accepted

### How does one create a draft in a room (with a single window)?

For simple ventilation, opening a single window may not mean a lot of circulation. Air has to come in and out of the same window, so it just leads to eddies and turbulence next to the window, with ...
• 5,303
3 votes
Accepted

### Is a 3 Hz beat frequency from my neighbor's HVAC a sign of a malfunction?

A 3Hz pulsating hum-- noise that is getting louder and softer at 3Hz. Yes, I agree that would be quite annoying. Since this is a residential unit in the US, both the compressor and the fan are run ...
• 925
3 votes

### Rapidly cool a flue gas without water circulation

Your approach is not an unusual one, engine brakes to measure horsepower usually make use of such a method, but they use much bigger water barrels. To answer your questions: "Can I just fill a ...
• 1,164

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