Sistemas De Refrigeracvion

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Tutorial on Air Conditioning
All electrical appliances (TVs, refrigerators, light bulbs) that consume energy generate heat. The quantity of heat generated is approximately equal to the quantity of energy consumed. For example, a 100 watt light bulb that is on for 1 hour consumes 100 watt-hours of electricity and generates about 100watthours of heat. Normally, heat (which is just a form of energy) is not measured in watt-hours, but in units such as calories or joules or BTUs. The conversion from watthours is straightforward and is defined as: 1 watt-hour = 3.41 BTUs
(Note: watt-hours could also be expressed in calories or joules as 1 watt-hour = 860 calories or 1 watt-hour = 3600 joules, but we will use the units of BTUs)[Refer to tutorial on Power & Energy to understand the difference between power (watts) and energy (watt-hours)]. Referring back to the 100 watt light bulb example, the heat generated is as follows: Heat generated = 100 watt-hours x 3.41 BTUs/watt-hour Heat generated = 341 BTUs The 341 BTUs of heat generated must be removed from the building to keep the temperature inside the building from rising.To give you a feel for how much heat 341 BTUs is, we refer back to the basic definition of a BTU. A BTU (British Thermal Unit) is the amount of energy (heat) required to raise the temperature of 1 pound of water 1 degree Fahrenheit. If a gallon of water weights 7 pounds, then the heat generated from one 100 watt light bulb burning for 1 hour will raise the temperature of 1 gallon of water 48.7°F.
(1 gallon x 7 lbs/gallon x 48.7°F x 1 BTU/lb °F = 341 BTUs).

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With the above as background, let’s focus on the heat generated by a computer monitor and the requirements on the air conditioning system. A typical monitor uses approximately 1 amp of current, which at 120 volts is 120 watts of power.Assuming an installation of 100 PCs, we can calculate the heat generated each hour: Hourly Heat Generated = 100 PCs x 120 watt-hours/PC x 3.41 BTUs/watt-hour Hourly Heat Generated = 40,920 BTUs Each hour the 100 PCs would generate 40,920 BTUs. Therefore, the air conditioner would have to provide 40,920 BTUs of cooling each hour to keep the inside temperature from rising. Air conditioners are measuredin “tons” of cooling where 1 ton equals 12,000 BTUs of cooling per hour. Therefore, the 100 PCs would require 3.4 tons of cooling. This is approximately the size of an air conditioner required for a 3000 square foot house—to cool the entire house! As you can see, there is quite a bit of heat generated by the monitor. Multiply this by 10 or 20 for a 1000 or 2000 PC installation and you can see theload on the air conditioning system. Air conditioning is not free–it uses electricity. To calculate the energy cost of air conditioning, the efficiency of the system needs to be known. System efficiency is known as the “K factor” and is a component in the Energy Analysis Program. Before we calculate the energy cost of running an air conditioner, let’s spend some time on what an air conditioneris. An air conditioner is basically a heat pump; it pumps heat from a cold region (the inside of the building that you are trying to keep cool) to a warm region (outside). Normally heat wants to move from warm regions to cold regions. To reverse this natural flow of heat, the air conditioner must pump the heat outside, which takes energy. Old (inefficient) air conditioning systems would requireabout 1 BTU of energy to remove 1 BTU of heat. This is a performance factor of 1 (K = 1 in Energy Analysis Program).

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High efficiency air conditioning systems may require as little as 0.33 BTUs of energy to remove 1 BTU of heat. This is a performance factor of 3 (K = 3 in Energy Analysis Program). Typical...