HRV Information

[Engineer6512]

I'm doing some research on a company that designs and manufactures Heat-Recovery ventilation systems (HRV)s. Rather than simply using an exhaust fan, the air is first passed through a heat exchanger to heat up the incoming air.

Is it true that this is relatively new technology? Are there products out there already that take this one step further and incorporate a furnace/air conditioner in the same unit?

 

[ChasBean1]

Beazley -

You name it, it's probably been done somewhere. Most popular heat recovery systems that I see are closed water/glycol loops recirculating water between the exhaust and make-up air streams.

The heat recovery wheel is also used (sparsely in my area). The wheel rotates between the exhaust and make-up air streams to transfer heat. It does a good job in heat transfer, but can also contaminate the make-up air stream in some circumstances if a dirty exhaust stream is used for heat recovery.

The technology is probably over 20 years old but I'm not a historian of it. ASHRAE Handbook of Fundamentals or Applications might help in this area. The systems I've seen are custom built, i.e., there is not a "heat recovery unit," but a coil in a custom exhaust air handling unit (EAHU) and a heat recovery coil added just after the mixing plenum in the supply AHU. The system uses a pump to circulate the water continuously between the two during the right outside air conditions.

I've also seen cogeneration plants using engine exhaust air to heat an LP boiler to produce steam for building services.

To answer your question best, I would say that the technology is not new, but the production and packaging of the technology in a way that your particular vendor advertises might be a new way to simplify the process.

I hope some of this input helps. -CB

 

[VEEKRISH]

Hello Beazley,
The technology is by no means new. We in India have been doing this for a long time, particularly in the Northen Parts, where the temperature during winters are close to zero at nights. The hot air is exhausted out via a water to air / glycol to air heat exchanger. The heated fluid is then pumped to another heat exchanger which is installed in the Fresh Air intake. This helps reduce heating costs. Very important in a developing country like ours.
Of late we also use the Heat Recovery Wheel, which Chasbean1 has talked about. I also agree with Chasbean1 that you need to check if there are problems of contamination (particularly in Pharma / Hospital applications)before applying this concept.

 

[briand2]

Beazley,

An alternative technology, plate heat exchangers, has not yet been mentioned. These can easily be built right into the supply/exhaust air handling unit. I have specified/used them on several occasions (in the UK).

Brian