Cooling Load Calc Pbl Pdf

A Self-Learning Report On

“COOLING LOAD ESTIMATION OF KITCHEN ROOM" For the subject of REFRIGERATION AND AIR CONDITIONING.

Under the guidance of Prof. N S Aaher. By Sr. No. 1

Batch T10

Class & Div. TE-C

Roll No. 203

Name GAIKWAD RAVINDRA

2

T10

TE-C

204

GEODERAO GAURAV

3

T10

TE-C

205

GHUGE GANESH

4

T10

TE-C

206

GEORGE MAYUR

Prof. N S Aaher. (Guide)

Sign

Dr. A. G. Thakur. Vice Principal and Head Mechanical Engineering Department.

Program Educational Objectives (PEO) (PEOs) of the Mechanical Engineering are established and are as follows: I. To prepare students for successful and efficient careers in industry that meet the needs of Indian and multinational companies. II. To develop the ability among students to synthesize and analyze data and technical concepts for application to product design and development. III. To provide opportunity for students to work as part of teams on multi-disciplinary projects. IV. To provide students with a sound foundation in the mathematical, scientific and engineering fundamentals necessary to formulate, solve and analyze engineering problems and to prepare them for higher studies, civil services etc. V. To promote awareness among students about life-long learning and to introduce them to professional ethics and codes of professional practice. VI. To inculcate in students ethical values and belongingness towards society. VII. To provide an opportunity to undertake innovative projects and research. VII. To make students aware of the latest developments in engineering and technology.

Program Outcomes (POs) At the end of this program graduates will be able to a) Demonstrate ability to apply basic knowledge in mathematics, science and engineering. b) Demonstrate the ability to conduct experiments, interpret and analyze data, and report

results. c) Demonstrate the ability to design mechanical systems, in general and a thermal system or

a process that meets desired specifications and requirements. d) Demonstrate the ability to function in a team as a member or leader. e) Demonstrate the ability to identify, formulate and solve Mechanical Engineering

problems. f) Demonstrate an understanding of their professional and ethical responsibilities. g) Communicate effectively in both verbal and written forms. h) Have the confidence to apply engineering solutions in global and societal contexts. i)

Capable of self-learning.

j)

Familiar with modern engineering software tools and equipments to analyze mechanical engineering problems.

k) Capable to demonstrate creativity.

l) An ability to prepare design documentations and to make effective presentations.

Aim: PROBLEM BASED LEARNING. Subject: REFRIGERATION AND AIR CONDITIONING. Topic: COOLING LOAD ESTIMATION OF KITCHEN ROOM. Steps: 1) Form the team. 2) Study the theory related to it. 3) Permission and appointment of visit from Milk processing plant. 4)Analysis of different types of Heat load. 5) Study all aspects regarding Refrigeration and Air conditioning. 6) Interact with cooled storage and make visit report. 7) Present report in the class. 8) Questions and answers. 9) Report.

Mapping:

Steps

Activity

PEO

PO

1

Form the Team.

III

d

2

Study the theory related to it.

II,IV

a, e, i

3

Solve the problem Psychrometric chart.

4

solve the problem analytically.

5

compare the analytical and II,III,VII experimental data and prepare result table.

a, b, g, l, k

6

Present in front of audience.

III,V

g, l

7

Questions and answers.

III

g, l

8

Report.

using VII, IV

VII, IV

j

e, j

Aim: Cooling load estimation of kitchen room. ABSTRACT Human comfortness is essential now a day because of the improvement in life style and increasing atmospheric temperature. Electrical air conditioning machines are not most suitable for large buildings because of the higher power consumption and shorter life. Central air conditioning is more reliable for easy operation with a lower maintenance cost. With large buildings such as commercial complex, auditorium, office buildings are provided with central air conditioning system. Educational and research institutions also need human comfortness, as the population of student community increase year by year. The effective design of central air conditioning can provide lower power consumption, capital cost and improve aesthetics of a building. Cooling load items such as, people heat gain, lighting heat gain, infiltration and ventilation heat gain can easily be putted to the MS-Excel programme. The programme can also be used to calculate cooling load due to walls and roofs.

1. Introduction Applying mechanical and thermal engineering concepts, an air conditioner was designed for the human comfort and other necessary objection. This project report delineates norms and the procedure for the estimation of the heat load on the air conditioner. Being socially conscious technocrat I choose to invest my time, effort, and engineering knowledge into clearly understanding the mechanism underlying within the air conditioner which became a necessity in today’s world .We chose to concentrate more on cooling load calculations because through this we can understand the heat gain sources so that we can have check on them the next time we switch on an A.C.

1.1 REFRIGERATION The term "refrigeration" may be defined as the process of removing heat from a substance under controlled conditions. It also includes the process of reducing and maintaining the temperature of a body below the general temperature of its surroundings. The device that serves this purpose is called "refrigerator". Refrigerator has become a part of day –to-day life of man. It has become a necessity in this world of technology. In other words the term refrigeration means continued extraction of heat from a body whose temperature is below the surrounding temperature. The refrigerant is a heat carrying medium which during their cycle in the refrigeration system absorbs heat from a low temperature system and discards it to high temperature body. There are many types of refrigerants that are widely being used. Some of them are Freon-22, R134a, R-11, R-12, R-100, etc .

1.2 AIR CONDITIONING

Merely lowering or raising the temperature provides comfort in general to the machines or its components and living beings in particular. In case of machine components along with temperature, humidity also has to be controlled and for the comfort of human beings along with these two important parameters, air motion and cleanliness also play a vital role. Air conditioning works on the same principle as that of Refrigerating system. Air conditioning is that branch of engineering science that deals with the conditioning of air

1.2. Terminology a) Refrigeration: - the term ‘Refrigeration’ means process of removing heat from a substance or space under the controlled conditions. It also include the process of reducing and maintaining the temperature of a body below the surrounding temperature b) Unit of refrigeration: - the practical unit of refrigeration is expressed in terms of ‘tonne of refrigeration (TR)’. A tonne of refrigeration is defined as the amount of refrigeration effects produced by the melting of 1 ton of ice from and at 0 oC in 24 hours. c) Coefficient of performance (COP): - the COP is defined as the ratio of heat extracted in the refrigerator to the work done on the refrigerant. d) Refrigerant: - refrigerant is the fluid used for heat transfer in a refrigerating system that release heat during condensation at a region of higher temperature and pressure, and absorbs heat during evaporation at low temperature and pressure region. e) Air conditioning: - controlling and maintaining environmental parameters such as temperature, humidity, cleanliness, air movement, sound level, pressure difference between condition space and surrounding within prescribed limit. f) CLTD: - cooling load temperature difference is an equivalent temperature difference used for calculating the instantaneous external cooling load across the walls and roofs.

g) Humidity: - it is the mass of water vapour present in 1 kg of dry air, and is generally expressed in terms of gram per kg of dry air (g/kg of dry air). It is also called specific humidity or humidity ratio. h) Relative humidity (RH): - it is a ratio of actual mass of water vapour in a given volume of moist air to the mass of water vapour in the same volume of saturated air at the same temperature and pressure. i) Dry bulb temperature (DBT): - it is the temperature of air recorded by thermometer, when it is not affected by the moisture present in the air. The dry bulb temperature is generally denoted by td or tdb. j) Wet bulb temperature (WBT): - it is the temperature of air recorded by a thermometer, when its bulb is surrounded by a wet cloth exposed to the air. The wet bulb temperature is generally denoted by tw or twb. k) Dew point temperature (DPT): - it is the temperature of the air recorded by the thermometer, when the moisture present it beings to condense. l) Heat transfer coefficient: - it is the rate of heat transfer through a unit area of building envelope material, including its boundary films, per unit temperature difference between the outside and inside air. m) Thermal resistance: - it is the reciprocal of the heat transfer coefficient and is expressed in m2-K/W. n) Sensible heat gain: - direct addition of heat to the enclosed space, without any change in its specific humidity, is known as sensible heat gain. o) Latent heat gain: - heat gain of space through addition of moisture, without change in its dry bulb temperature, is known as latent heat gain. p) Space heat gain: - it is the rate of heat gain, at which heat inter into and generated within the conditioned space. q) Space cooling load: - it is the rate at which energy must be removed from a space to maintain a desired air temperature of space.

2. Literature Review The basic concept behind air conditioning is known to have applied in ancient Egypt, where reeds were hung in windows and were moistened with trickling water. The evaporation of water cooled the air blowing through the window. This process also made the air more humid Anderson et al. [1] designed heating and cooling loads for a sample residential building at different orientations, using a development version of the building energy analysis computer program BLAST. They identified that the total loads were found to be higher for north than south orientation except in extreme southern latitudes of the U.S. Omar et al. [2] calculated the hourly cooling load due to different kinds of wall, roof and fenestration using transfer function method (TFM). The output of this method was compared with the well-known Carrier program and the results were acceptable. In the case of cooling load, when the results were compared with the ASHRAE examples, some differences were noticed due to wall and roof. They also studied the effects of changing the wall color on cooling load. Adnan Shariah et al. [3] studied the effect of the absorptance of external surfaces of buildings on heating, cooling and total loads using the TRNSYS simulation program. Two types of construction materials, namely heavy weight concrete block and light weight concrete were used in the simulation. They also calculated the effects of the absorptance on energy loads for uninsulated buildings. They reported that, foruninsulated buildings, as the absorptance was changed from one to zero, the total energy load decreased by 32%, while for insulated buildings, it decreased by 26% inAmman. Whereas the decrease was about 47% for uninsulated and 32% for insulated buildings in Aqaba. Kulkarni et al. [4] optimized cooling load for a lecture theatre in a composite climate in India. the lecture o

o

theatre had a dimension of 16m×8.4m×3.6m and was situated at Roorkee (28.58 N, 77.20 E) in the northern region of India. The monthly, annual cooling load and cooling capacity of air conditioning system was determined by a computer simulation program. They reported that the use of false celling, ceramic tiles on roof and floor, electro chromic reflective colored, 13mm air gap, clear glass gave the best possible retrofitting option.

Source of heat load The source may be give out sensible heat load or latent heat load A)External heat load:1) Solar heat gain through glass. 2) Heat gain through opaque surface like wall , roof ,floor etc. 3) Infiltration. 4) Ventilation.

B) Internal Load 1) Occupancy. 2) Equipment. 3) Product brought.

1 System heat gain This is the load due to air conditioning system itself. It is three types, Duct heat gained: cool air in the duct absorber heat from outside atmosphere trough duct wall. Duct air leakage: the joints of duct air likely to be leakage. This loss of air would result introduction of load. Blower power: the blower or fan which circulate air through the complete system expands its power in supply air as heat.

2 Heat gain through glass Heat is transmitted through glass due to solar radiation this could be direct in the form of sun rays diffused radiation due to deflection of other object out side Solar heat gained =solar radiation intensity*area of window glass.

3 Heat load trough opaque surface The tempreture difference across wall roof, floor, and other surfaces like glass cover heat transfer through this surface heat from outside air transferred meanly by convection to outer through structure to inside surface this is calculated by formula H=UA(T2-T1) Where, U=overall heat transfer coefficient A=surface area (T2-T1)=tempreture difference 4 Infiltration Tis load is due to air that enters the room by various reason and bring along with it to the SH and LH load this infiltration of air is normal application is mainly due to this reason a) through crank in window b) due to opening of door

5 Outside air load Both infiltration and ventilation are heat load due to out side air the infiltration load is directly in the space and ventilation load is directly on coil . Outside air sensible heat is to be calculate as 0.0204(mm/person*no of occupant*change in temp *10^3) Outside air latent heat is to be calculated as 50(mm/person* no of person* change in temp*10^3).

6 Ventilation Human being inside a space required fresh ness to air it has been study by ASHRAE that inadequate fresh air supplied to the space leads to health problem for people inside it this is called as sick building syndrome. Therefore ASHRAE gives minimum and recommended values of fresh air per person for different application of the space.

7 Occupancy heat load Human being constantly gives out heat to maintained body temperature in an air conditioning room ,sensible heat load gives out due to temperature difference between body and room air. The value of heat load increases with in the activity of human being Total SH=sensible heat /person*no of occupant Total LH=latent heat /person *no of occupant

8 Lightning Lightning power supply finally generates heat in the room it is only sensible heat.

HVAC system design The main objectives of HVAC system design are as follows a) Control of temperature, humidity, air purity and correct pressurization to avoid contamination. b) Provide comfort and healthy indoor environment of office buildings, educational buildings, cinemas, libraries, auditoriums, multiplex, shopping centers, hotel, public place, c) Provide special air filtration to remove bacteria, high indoor quality, avoid cross contamination.

Cooling load calculation The objectives of cooling load calculation are as follows a) To determine be the optimum rate at which heat needs to be removed from space to establish thermal equilibrium & maintain a pre-determined inside conditions. b) To calculate peak design loads (cooling/heating). c) To estimate capacity or size of plant/equipment. d) To provide info for HVAC designs e.g. load profiles. e) To form the basis for building energy analysis.