Sunday, July 18, 2010
Friday, July 9, 2010
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Monday, January 4, 2010
Global Warming
New projections by the US-based Massachusetts Institute of Technology (MIT) show that mean global temperature could increase by as much as 5.2oC this century if "rapid and massive action" to reduce greenhouse gas emissions is not taken, according to a press release. Previous studies have indicated an increase of 2.4oC.
Various studies have shown that a rise of 2oC in global temperatures would probably destroy 30% to 40% of all known species, generate bigger, fiercer and more frequent heat waves and drought, more intense weather events like floods and cyclones, and would rise the sea level by at least a metre, displacing millions.
The new projections, published in the American Meteorological Society's Journal of Climate, indicate a 90% chance of the temperature increasing b between 3.5oC and 7.4oC during the next 100 year.
Various studies have shown that a rise of 2oC in global temperatures would probably destroy 30% to 40% of all known species, generate bigger, fiercer and more frequent heat waves and drought, more intense weather events like floods and cyclones, and would rise the sea level by at least a metre, displacing millions.
The new projections, published in the American Meteorological Society's Journal of Climate, indicate a 90% chance of the temperature increasing b between 3.5oC and 7.4oC during the next 100 year.
Cooling Tower
- Cooling Tower Function -
A cooling tower transfers heat from warm water (such as condenser water) to a stream of air by bringing them into direct contact and using the cooling effect of the process of evaporation. Thus in many climates a cooling tower is able to economically cool water to about 25oC which is lower than can be achieved in a dry air heat exchanger under similar ambient conditions. This extra cooling ability can translate to as much as 20% reduction in input power required, or an equivalent improvement in coefficient of performance (COP), of the plant or system being cooled.
Typically the space and the fan power requirements for air cooled condensers and other forms of dry coolers is nearly twice that of the equivalent cooling tower, including water pumping power.
For refrigeration systems, direct evaporative water cooling, with a shell and tube condenser, can reduce system annual energy consumption by 15% when compared to dry air condenser cooling. One type of cooling tower, the evaporative condenser, with in-built condenser coil can reduce refrigeration system energy consumption by a further 5% as there is one less heat exchanger process involved.
Although cooling towers provide significant energy saving compared to dry air cooling, their overall operational costs including servicing and the correct water treatment, may exceed that of dry air cooling in small systems, particularly in areas of relatively low design dry-bulb temperature. Air cooled condensers may also be used in preference to cooling towers in areas where available water supply is of poor quality or which have sustained high wet-bulb temperature. Selection of the most appropriate heat rejection system will depend on the water temperature needed, energy saving, space available and the operational costs for the particular application.
-- to be continued --
A cooling tower transfers heat from warm water (such as condenser water) to a stream of air by bringing them into direct contact and using the cooling effect of the process of evaporation. Thus in many climates a cooling tower is able to economically cool water to about 25oC which is lower than can be achieved in a dry air heat exchanger under similar ambient conditions. This extra cooling ability can translate to as much as 20% reduction in input power required, or an equivalent improvement in coefficient of performance (COP), of the plant or system being cooled.
Typically the space and the fan power requirements for air cooled condensers and other forms of dry coolers is nearly twice that of the equivalent cooling tower, including water pumping power.
For refrigeration systems, direct evaporative water cooling, with a shell and tube condenser, can reduce system annual energy consumption by 15% when compared to dry air condenser cooling. One type of cooling tower, the evaporative condenser, with in-built condenser coil can reduce refrigeration system energy consumption by a further 5% as there is one less heat exchanger process involved.
Although cooling towers provide significant energy saving compared to dry air cooling, their overall operational costs including servicing and the correct water treatment, may exceed that of dry air cooling in small systems, particularly in areas of relatively low design dry-bulb temperature. Air cooled condensers may also be used in preference to cooling towers in areas where available water supply is of poor quality or which have sustained high wet-bulb temperature. Selection of the most appropriate heat rejection system will depend on the water temperature needed, energy saving, space available and the operational costs for the particular application.
-- to be continued --
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