R&AC Lecture 32 - Lesson 32 Cooling And Heating...

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Unformatted text preview: Lesson 32 Cooling And Heating Load Calculations - Estimation Of Solar Radiation Version 1 ME, IIT Kharagpur 1 The specific objectives of this lecture are to: 1. Introduction to cooling and heating load calculations ( Section 32.1 ) 2. Solar radiation, solar constant and solar irradiation ( Section 32.2 ) 3. Solar geometry, latitude, declination, hour angles, local solar time and total sunshine hours ( Section 32.2.4 ) 4. Derived solar angles ( Section 32.2.5 ) 5. Angle of incidence for horizontal, vertical and tilted surfaces ( Section 32.2.6 ) 6. Calculation of direct, diffuse and reflected radiation using ASHRAE solar radiation model ( Section 32.3 ) 7. Effect of clouds ( Section 32.4 ) At the end of the lecture, the student should be able to: 1. Explain the need for cooling and heating load calculations 2. Explain the importance of solar radiation in air conditioning 3. Define solar angles namely, latitude, declination and hour angles and calculate the same and estimate the time of sunrise, sunset and total sunshine hours at a given location on a given day 4. Define derived solar angles and express them in terms of basic solar angles 5. Calculate the angle of incidence for surfaces of any orientation 6. Estimate direct, diffuse, reflected and total solar irradiation incident on surfaces of any orientation using ASHRAE models 7. Explain the effects of clouds on incident solar radiation 32.1 Introduction: The primary function of an air conditioning system is to maintain the conditioned space at required temperature, moisture content with due attention towards the air motion, air quality and noise. The required conditions are decided by the end use of the conditioned space, e.g. for providing thermal comfort to the occupants as in comfort air conditioning applications, for providing suitable conditions for a process or for manufacturing a product as in industrial air conditioning applications etc. The reason behind carrying out cooling and heating load calculations is to ensure that the cooling and heating equipment Version 1 ME, IIT Kharagpur 2 designed or selected serves the intended purpose of maintaining the required conditions in the conditioned space. Design and/or selection of cooling and heating systems involve decisions regarding the required capacity of the equipment selected, type of the equipment etc. By carrying out cooling and heating load calculations one can estimate the capacity that will be required for various air conditioning equipment. For carrying out load calculations it is essential to have knowledge of various energy transfers that take place across the conditioned space, which will influence the required capacity of the air conditioning equipment. Cooling and heating load calculations involve a systematic step-wise procedure by following which one can estimate the various individual energy flows and finally the total energy flow across an air conditioned building....
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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 32 - Lesson 32 Cooling And Heating...

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