China Researchers Tweak Chiller Potential
This was demonstrated less than two years ago when the International Institute of Refrigeration held its once-every-four-year International Congress of Refrigeration. The event took place in Beijing and drew an especially large number of researchers and scientists from China to that country’s capital.
More than 800 papers were presented from researchers throughout the world on all matters related to cooling, heating, and refrigeration. Among those were several dozen from China researchers that focused on chillers.
The following is a brief overview of some of those papers to give some idea of the kind of chiller projects underway in China.
One team of researchers said that overall “developments of advanced absorption refrigeration theory and technology have been achieved in China recently.” They cited “many advanced types of lithium bromide absorption chillers (that) have been manufactured on a large scale including direct-fired double-effect, hot water-operated, two-stage, and waste-heat operated.”
In an energy-saving move in China, researchers there have developed a lithium bromide absorption chiller/heater that they said could utilize various kinds of energy such as solar, exhaust heat, underground water, natural gas, and diesel oil. “It can realize the triple-function cooling, heating, and hot-water supplying,” they said.
In another study involving lithium bromide, an absorption chiller was changed from water-cooled to air-cooled by changing the structure of the evaporator, cooler, and absorber.
Yet another researcher said that to achieve better chiller efficiency and reliability, control of entering condenser water temperature is recommended. His research involved what he said was three optimized water system designs to either recover more heat or achieve higher heating water temperature.
Also being experimented with in China is a four-bed adsorption chiller using silica gel and water, operating with both heat and mass recovery schemes so as to enhance cycle performance. “The adsorption chillers have the advantage of employing low-temperature waste heat which is available in abundance in the process industry,” it was reported.
A two-bed adsorption chiller using silica gel adsorbent and water was developed by another team for recovery of low-grade waste heat. According to the team, “These experiments were conducted at the cyclic steady state with constant heat source and control temperatures.”
THE SOLAR SIDEOne researcher said that “Using solar energy as a heating source for the solar absorption refrigerating system can reduce the consumption of the conventional energy and lessen the environmental pollution, which accords to the principle of sustainable development.” His paper went on to describe some of his research.
Meanwhile, using dry air, not electricity, was the concept of an indirect evaporative chiller. In this case, said the five-person research team, the produced water’s ideal temperature is close to the dew point of the inlet air. In the chiller developed and tested, “the temperature of the cold water is more or less at the middle of the outdoor dew point and web bulb temperature.” The technology was being used in at least 10 large buildings in the Sinkiang province.
Another study reported on how several heat exchangers can be configured to minimize the size of an air-cooled water chiller. It was noted, “Different configurations of the heat exchangers will affect the flow distribution across the heat exchangers significantly. The pressure loss thus affected will also cause the change in the total airflow through the heat exchangers.” The study used an air-cooled chiller for comparison when the configuration of the heat exchanger is varied. It was found that the condenser configuration could be changed to increase 9.5 percent for airflow and 6.2 percent for heat transfer.
In another smaller configuration, an adsorption chiller and a gas-driven generator are part of a micro-combined cooling, heating, and power (CCHP) system. The CCHP system uses natural gas and liquefied petroleum. Silica gel-water is used as part of the adsorption system. Researchers contended the overall thermal and electrical efficiency is more than 70 percent.
Publication date: 05/11/2009