SRU SERIES WASTE HEAT RECOVERY UNITS

PRINCIPLE

The waste heat recovery unit is designed to transfer the waste heat from the forced draft heating unit into usable heat. The waste flue gases from the heating unit are redirected to the recovery unit, which is placed beside the heating unit or alongside the unit's chimney. The recovery unit cools the flue gases to the point where sensible as well as latent heat is recovered.

The waste heat recovery unit is a finned tube heat exchanger. The hot waste flue gas is diverted into the bottom receiver of this unit and then flows upwards across and through a series of specially designed finned tubes. The water that is being heated flows on the inside of these tubes. The SRU series is designed so that waste flue gas temperatures even below the water dewpoint (58C - 136) can be reached.

NATURAL GAS FACTS

Each pound of natural gas has a heat value of approximately 22,000 BTU. When natural gas is burnt, each pound of gas produces about 2 pounds of moisture (steam) with a heat value of 2400 BTU. Therefore the BTU lost during combustion of a pound of natural gas is about 11%. 2,400 BTU/lb = 11% loss 22,000 BTU/lb

POTENTIAL SAVINGS WITH SRU WASTE HEAT RECOVERY

For a typical 250 HP natural gas fired boiler operating with an exhaust gas temperature of 410F and 15% excess combustion air the efficiency is approximately 80%. The fuel input is approximately 10.5 million BTU/hr, and 20% of the fuel's total energy is available for recovery. By incorporating a SRU waste heat recovery system to produce 104F water, about 15% of the fuel's original energy can be recovered. If the boiler operates for an equivalent of 6,000 full load hours per year, and natural gas costs $.50 therm, the annual savings realized from a SRU waste heat recovery system would be: 10.5M BTU/hr x 15% x 6,000hrs/yr x $5.00/M BTU* = $47,400

*1 M BTU = 10 therm

APPLICATIONS

The key to the successful application of heat recovery is the ability to put the recovered heat to use. Two primary uses for recovered heat are domestic water heating and space comfort heating. Other uses include laundry wash water, industrial process water and district heating systems.

Potential Applications include: Greenhouses - Hospitals and Health Centers - Food processing - Schools and Universities - Laundries - Breweries - Hotels - Wineries - Government Buildings - Swimming pools.

CONDENSATE

Condensation of water vapor from the flue gases results when the water outlet temperature is below the dewpoint of the flue gas. Naturally the lower the flue gases can be cooled, the higher the performing efficiency of the waste heat recovery unit. When the temperature of the waste flue gas is lowered beyond 133F condensation occurs. The waste heat recovery unit is designed for natural gas or propane fired equipment only. When the heating unit is required to operate on oil the flue gases will have to be bypassed from the waste heat recovery unit. The vertical construction of the SRU waste heat recovery unit provides for the best possible use of available space. This design also allows the condensate to flow down from the top rows of tubes in the recovery unit, providing a self-cleaning action of the aluminum fin tubes.

HEATING TUBES

The SRU waste heat recovery unit has a large gas-side heat transfer surface of aluminum fin tubes, with the fins and the tubes formed as one piece. Pure aluminum is a very good heat conductor; is it also exceedingly resistant to the mildly acidic flue gas condensate. The aluminum fin tubes are fitted around a stainless steel tube. Stainless steel is used to prevent corrosion on the waterside surface. Compared to other materials, stainless steel will not allow the build-up of iron particles, which would act as an insulator on the tube surface.

FLUE GAS RESISTANCE

Because of the high conducting properties of aluminum, the fins on the heating tubes are very thin. This allows more room for the flue gases to pass through. The result is an optimal ratio of the flue gas flow with respect to the fin surface area, which keeps the resistance of the flue gas heated side low. Because there is only a small increase in pressure, in most cases the heating unit is still capable of using its existing blower fan.

CAPACITY

Standard sizes are available for equipment with inputs from 2.1 to 42 million BTU per hour. All units are constructed in accordance with the ASME codes.

BENEFITS

E-mail, fax or call us with a description of your heat source and potential energy application, using the enclosed data input sheet and we will be happy to tell you what a SRU waste heat recovery unit can do to reduce your company's operating costs.

Various Benefits include: Increased system efficiency (typically 90-95%) - Cost savings (typically 10-15%) - Short payback - Easy installation, low maintenance - Reduced particulate, water vapor and noxious gas emissions - Reduced stack noise emission - Operates over a broad range of equipment conditions - Computer-aided design (to ensure optimum sizing) - Computer-aided investment analysis - 7-year limited guarantee