Energy Information Water-cooled air compressors consume water almost constantly, and therefore the amount of water they require depends on equipment operating times. As mentioned above, domestic water use drops significantly (in some cases to nearly zero) when using an aircooled system. Only during the summer, when the cooling requirements are high, is domestic water required to supplement the air cooling. The cost of the electricity required to operate an air-cooled system is 4 to 6 percent of the cost of water at typical municipal rates. The only drawback of the system is that the cooling water inlet temperature needs to be kept as low as possible. Manufacturers specify an inlet temperature of 12°C for a water-cooled system. However, it is difficult to achieve such a low glycol temperature year-round. If an average inlet temperature is 20°C, a twostage system with inter-cooling and after-cooling would require a 2-3 percent higher input of energy. One side benefit of the air-glycol system is that it preheats ventilation or combustion air from the fan system heat exchanger in the winter.
Case StudySimon Fraser University in Burnaby, British Columbia, has implemented a program to reduce domestic cold water use. The compressed air system consists of three permanently installed Atlas Copco ZR series two-stage rotary compressors, one of which is used for standby capacity. The two remaining compressors operate 24 hours a day, year-round. The existing cooling system for the compressors was modified to include a new glycol loop, an air-glycol heat exchanger and a supplemental municipal water heat exchanger for peak periods. The maximum heat rejection of the compressors is 130.6 kW during standard operation. The cooling loop was designed with a maximum inlet temperature of 30°C, a maximum temperature rise of 15°C and a glycol mixture flow rate of 2.14 litres per second. A bank of four 1-hp (0.746 kW) fans draws outside air through the air-glycol heat exchanger, and a pair of 2-hp (1.492 kW) circulation pumps each rated at 2.33 L/s (37 U.S. gallons per minute), provides flow through the heat exchanger and to the compressors. The pumps are set to run in a lead/lag configuration, with the second pump running only if the first pump fails. The four fans are configured in pairs and are cycled to maintain the cooling loop temperature setpoint. Table 1 analyses the project cost and savings, and shows that the project will yield a 2.3-year simple payback. Water savings values are based on meter readings performed before the project was implemented.
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Water Cooled Evaporative Air Conditioning
ReplyDeleteAlthough water is used to assist with cooling, this technology is not related to the conventional Evaporative Air Coolers often called swamp coolers. Water is used to remove heat from the refrigerant and at the same time reduce the work of the compressor. The Water Cooled Evaporative Air Conditioner is a residential application of a technology already in use in commercial buildings for split system air conditioners known as chillers. Think of this technology as a mini-chiller for residential use.
Evaporative cooled condensing units for split system air conditioners have a number of advantages over air-cooled units. This is why most commercial air conditioners larger than about 250 tons typically rely on cooling towers to cool water and remove heat generated from the compression cycle of the chiller. The key elements of the unit include multiple low-pressure water nozzles that spray a mist of water over the condenser coils to remove heat after the refrigerant is compressed. Water temperature can be maintained at about 10° F over wet bulb via heat absorbed through evaporation, which is then removed via a fan on top of the unit.
Unlike air cooled units, which lose in the range of 25 percent of their rated efficiency at temperatures exceeding 100° F relative to their SEER rating, the efficiency of an evaporative water cooled unit has a minimal drop.
In the past, evaporative cooled condenser units were used only in commercial applications. Now one manufacturer has a model that is designed specifically for the residential market.
Freus Inc. has developed a water cooled evaporative condenser unit. A "scroll" compressor compresses the R-22 refrigerant. A small water pump continually sprays water over the condenser coil, which cools the coil primarily via conduction from the copper coil to the water, sprayed on the coil. The coil is solid copper; approximately three times the thickness (i.e. 0.032" vs. 0.012") of that used in air-cooled condensers, and the copper is coated to prevent corrosion. Magnesium anodes are included to treat the water and reduce coil corrosion.
A float maintains approximately 3.5 inches of water in the bottom of the condenser. Every 8 hours of run time, a timer causes a purge pump to pump all water from the bottom of the unit (approximately 5-8 gallons). The float valve then causes more water to flow until a level of about 3.5 inches is restored.
Water removes heat from the condenser coils far more efficiently than air. The heat transfer and evaporative process is increased via a fan on top of the condenser.
Above 95° F, a typical air cooled condenser draws approximately an additional 10% power for each 10° F increase in temperature. In contrast, an evaporative cooled condenser draws about the same power over a wide range of outdoor temperatures.
Residential and small commercial models are available from 2 to 12 tons. The dimensions of the evaporator unit are comparable to a 3-5 ton conventional condenser unit.
Inverter-driven systems can promote maximum compressor efficiency in term of smooth operation. The system can detect subtle fluctuations in temperatures and adjust its capacity output automatically which lead to constant stable temperature while minimizing power consumption and promoting humidity control.
ReplyDeleteInverter system can control over room temperature to deliver appropriate capacity which is smart technology that can suitably match cooling and heating performance with operating requirements at specific location so the system can ensure that a room will be never too hot or too cold.
Conventional compressor operate at a fixed speed with on and off repetitively, on the other hand, inverter compressor has controller which can control power output to fit with variable operating environment as well.
Inverter Benefits:
1.) Precision Temperature Control : less noticeable swing in temperature because of its adaptation of capacity to match with any variable conditions automatically
2.) High Efficiency : deliver only the energy needed to satisfy the cooling or heating condition, thereby saving both energy and cash
3.) Humidity Control : enjoy greater comfortable climate
4.) Heating Performance : compressor rotation speed can greatly improve the heat exchanger performance between indoor and outdoor units
Inverter – Technology for the Future:
Inverter technology is becoming the new trend in HVAC&R industry. The system can enhance smoothing performance for any cooling or heating applications. For current situation, this technology can decrease the using of energy which not only save money but also friendly to the environment and create less global warming.
Combination of ‘Twin Mechanism’ with Inverter Technology ( TNB – DC Twin Rotary Compressor )
‘Twin Mechanism’
This advanced technology can result in the combination of highly powerful and smooth performance through the latest innovative solution of ‘Twin Mechanism’. This mechanism are done by balancing torque of two compression chambers in a revolution which can operate at the highest efficiency with extremely low vibration and low noise. Moreover, they are compact sizes, lightweight, and wider range of operating area than other rotary compressor. With our special design, we use selective raw material and meticulous process to ensure superior performance and reliability.
Our DC Twin Rotary Compressor is the combination of double technology solution which are ‘Twin Mechanism’ and ‘Inverter Technology’. This unique solution can ensure specifically for the highest smooth performance with quiet compressor operation and high energy saving when compare with other compressor running at the same operating area. Its compact sizes and lightweight are also comfortable for unit with space limitation but need for high compression speed.
Inverter compressor for HVAC systems
ReplyDeleteAn Inverter compressor is designed to vary its speed as the demands in the room change. Inverter compressors are designed to soft start therefore causing no dips in power supply.
Single phase AC power is supplied to the outdoor unit where it is rectified and converted into DC power to drive the compressor the input frequency is then modified to allow the compressor to run at a variety of speeds.
As the compressor speed decreases, the amount of refrigerant entering the indoor unit also decreases. This results in a more comfortable environment as the unit only produces the appropriate amount of cooling or heating required at that time - no more temperature swings.
Inverter compressors have been shown to reduce power consumption by as much as 60% when compared to conventional fixed speed equivalents.
The SPW DC inverters use Advanced Digital Hybrid (ADH) technology for better, smarter and more cost-efficient year-round climate control. Immediately following start up, the DC compressor operates at maximum power to provide almost instant heating or cooling. As the desired air temperature is reached, a special Pulse Width Module automatically adjusts the compressor's frequency to exactly meet the cooling or heating requirements of the room. The result is exceptionally precise temperature control, less noise and significant energy savings