R&AC Lecture 31 - Lesson 31 Evaporative, Winter And All...

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Lesson 31 Evaporative, Winter And All Year Air Conditioning Systems Version 1 ME, IIT Kharagpur 1
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The specific objectives of this lecture are to: 1. Introduce evaporative cooling systems ( Section 31.1 ) 2. Classify evaporative cooling systems ( Section 31.2 ) 3. Discuss the characteristics of direct evaporative cooling systems ( Section 31.2.1 ) 4. Discuss the characteristics of indirect evaporative cooling systems ( Section 31.2.2 ) 5. Discuss the characteristics of multi-stage evaporative cooling systems ( Section 31.2.3 ) 6. Discuss advantages and disadvantages of evaporative cooling systems ( Section 31.3 ) 7. Discuss the applicability of evaporative cooling systems ( Section 31.4 ) 8. Describe winter air conditioning systems ( Section 31.5 ) 9. Describe all year air conditioning systems ( Section 31.6 ) At the end of the lecture, the student should be able to: 1. Explain the working principle of direct, indirect and multi-stage evaporative cooling systems 2. Perform psychrometric calculations on evaporative cooling systems 3. List the advantages and disadvantages of evaporative cooling systems 4. Evaluate the applicability of evaporative cooling systems based on climatic conditions 5. Describe winter air conditioning systems and perform psychrometric calculations on these systems 6. Describe all year air conditioning systems 31.1. Introduction to evaporative air conditioning systems: Summer air conditioning systems capable of maintaining exactly the required conditions in the conditioned space are expensive to own and operate. Sometimes, partially effective systems may yield the best results in terms of comfort and cost. Evaporative air conditioning systems are inexpensive and offer an attractive alternative to the conventional summer air conditioning systems in places, which are hot and dry. Evaporative air conditioning systems also find applications in hot industrial environments where the use of conventional air conditioning systems becomes prohibitively expensive. Evaporative cooling has been in use for many centuries in countries such as India for cooling water and for providing thermal comfort in hot and dry regions. This system is based on the principle that when moist but unsaturated air comes in contact with a wetted surface whose temperature is higher than the dew point temperature of air, some water from the wetted surface evaporates into air. The latent heat of evaporation is taken from Version 1 ME, IIT Kharagpur 2
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water, air or both of them. In this process, the air loses sensible heat but gains latent heat due to transfer of water vapour. Thus the air gets cooled and humidified. The cooled and humidified air can be used for providing thermal comfort. 31.2. Classification of evaporative cooling systems: The principle of evaporative cooling can be used in several ways.
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This note was uploaded on 02/29/2012 for the course CHEMICAL 302 taught by Professor Nptel during the Spring '12 term at Birla Institute of Technology & Science.

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R&AC Lecture 31 - Lesson 31 Evaporative, Winter And All...

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