R&AC Lecture 29 - Lesson 29 Inside And Outside...

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Unformatted text preview: Lesson 29 Inside And Outside Design Conditions Version 1 ME, IIT Kharagpur 1 The specific objectives of this lecture are to: 1. Describe a typical air conditioning system and discuss the need for fixing suitable indoor and outdoor design conditions ( Section 29.1 ) 2. Discuss the criteria used for selecting inside design conditions ( Section 29.2 ) 3. Define thermal comfort, metabolic rate and response of human beings to variation in body temperature ( Section 29.3 ) 4. Present heat balance equation, equations for convective, radiative and evaporative losses from the skin, metabolic rates for various types of activities and discuss the thermo-regulatory mechanism used by human body to fight against heat and cold ( Section 29.4 ) 5. Discuss the factors affecting thermal comfort ( Section 29.5 ) 6. Discuss the various thermal indices used for evaluating indoor environment and present ASHRAE comfort chart, recommended inside design conditions and discuss the concept of Predicted Mean Vote (PMV) and Percent of People Dissatisfied (PPD) ( Section 29.6 ) 7. Discuss the criteria used for selecting outside design conditions and present typical summer design conditions for major Indian cities as suggested by ASHRAE ( Section 29.7 ) At the end of the lecture, the student should be able to: 1. Explain the need for selecting design inside and outside conditions with respect to a typical air conditioning system 2. Define thermal comfort, metabolism, metabolic rate and discuss the effects of variation in body temperatures on human beings 3. Write the heat balance and heat transfer equations from a human body and using these equations, estimate various heat transfer rates 4. List the factors affecting thermal comfort 5. Define the various thermal indices used in evaluating indoor environment 6. Draw the ASHRAE comfort chart and mark the comfort zones for summer and winter conditions 7. Select suitable indoor design conditions based on comfort criteria 8. Define PMV and PPD and explain their significance 9. Explain the method followed for selecting suitable outside design conditions Version 1 ME, IIT Kharagpur 2 29.1. Introduction: Design and analysis of air conditioning systems involves selection of suitable inside and outside design conditions, estimation of the required capacity of cooling or heating equipment, selection of suitable cooling/heating system, selecting supply conditions, design of air transmission and distribution systems etc. Generally, the inputs are the building specifications and its usage pattern and any other special requirements. Figure 29.1 shows the schematic of a basic summer air conditioning system. As shown in the figure, under a typical summer condition, the building gains sensible and latent heats from the surroundings and also due to internal heat sources (RSH and RLH). The supply air to the building extracts the building heat gains from the conditioned space. These heat gains along with other heat gains due to ventilation, return ducts etc. have to be along with other heat gains due to ventilation, return ducts etc....
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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 29 - Lesson 29 Inside And Outside...

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