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Volume: 01-Issue: 01, August 2014 ISHRAE-PSNA Student Chapter Newsletter Department of Mechanical Engineering

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  • Volume: 01-Issue: 01, August 2014


    Student Chapter


    Department of Mechanical


  • Warm Greetings

    Dear ISHRAEites, Students and Faculties

    Addressing you all through this ISHRAE- PSNA Student

    Chapter forum is a matter of immense pleasure and pride for me.

    The Indian Society of Heating, Refrigerating and Air

    Conditioning Engineers (ISHRAE), was founded in 1981 at New Delhi

    by a group of eminent HVAC&R professionals. ISHRAE becomes

    ‘International Associate’ of the American Society of Heating,

    Refrigerating and Air-conditioning Engineers (ASHRAE) in 1994.

    ISHRAE-PSNA Student Chapter was inaugurated in August

    2013 at our Department of Mechanical Engineering by a group of

    eminent HVAC&R professionals, Faculties and Student members.

    ISHRAE- PSNA Student Chapter mission is to protect the Environment,

    improve Indoor Air Quality, help Energy Conservation, and provide

    continuing education and career guidance to student members.

    ISHRAE-PSNA student chapter of Mechanical Engineering

    Department has been arranging various events such as seminars, quiz

    contests, guest lectures, plant and site visits to enhance students

    knowledge in the area of Heating ventilation and air conditioning,

    energy conservation, environmental concerns.

    I would like to bring out the details of the events that were

    conducted in the ISHRAE-PSNA student chapter of Mechanical

    Engineering Department during the period of August 2013 - 2014.

    I express my sincere gratitude to our management, Principal,

    Head of the Department, Faculties and students for their assistance in

    ISHRAE-PSNA student chapter activities.

    Best wishes and warm regards


    ISHRAE-PSNA Student Chapter-Department of Mechanical






    August 2013-2014

    Complied and Edited by Dr.G.R.Kannan; Publisher: PSNA College of Engineering and Technology


    Inauguration of ISHRAE-

    PSNA Student Chapter

    Guest Lecture

    NCRAC-2013, IITM

    Workshop at Anna


    Design competition for


    Bry air Awards for

    HVAC Excellence

    Student Articles


    Dr.G.R. Kannan


    ISHRAE-PSNA Student Chapter

    Faculty Advisors


    Mr. P.M. Venkateswaran,


    Mr. S.Venkat Sharma,


    Mr. Milan Thapa, Secretary

    Ms. Gaayathree, Treasurer



    Mr. R.V.Prasanth

    Mr. Suresh

    Mr. Bakhirathan Asokan

    Mr. Rakesh.S

    Mr. Upendra Sah Kalbar

    Volume: 01- Issue: 01, August 2014



    Bulletin board

    Inauguration of ISHRAE-PSNA Student

    chapter 2013-2014

    Inaugural function of ISHRAE (Indian

    Society of Heating, Refrigerating & Air-

    conditioning Engineers) was held on


    August 2013 at our Sri Rangalakshmi

    auditorium of PSNA College of engineering

    and Technology. ISHRAE-PSNA student

    chapter had been inaugurated with 60 student


    Office bearers and chapter working

    committee members were selected and taken

    oath for effective functioning of ISHRAE-

    PSNA Student Chapter. The details of office

    bearers and chapter working committee are

    given below.


    Mr. P.M. Venkateswaran, President

    Mr. S.Venkat Sharma, President Elect

    Mr. Milan Thapa, Secretary

    Mr. Gaayathree, Treasurer


    Mr. R.V.Prasanth

    Mr. Suresh

    Mr. Bakhirathan Asokan

    Mr. Rakesh.S

    Mr. Upendra Sah Kalbar

    Guest lecture

    ISHRAE PSNA Student chapter was

    conducted a Guest lecture titled as

    Professional ethics for air conditioning

    engineers by Mr. Shankar Rajasekaran-Zonal

    Chair ISHRAE Southern Chapter, Chennai

    on 07.08.2013 afternoon. The program was

    attended by about 60 student members.

    NCRAC-IIT- Madras

    Three students were attended


    National conference on refrigeration and

    air Conditioning (NCRAC-2013) at IIT

    Madras, Chennai from 12.12.2013 to

    14.12.2013. Selection of students for this

    conference was purely on the basis of

    technical quiz competition which was held in

    our ISHRAE-PSNA Student Chapter.

    The details of participants and their

    photos, participation certificates are given


    3) Mr.P.M.Venkateswaran

    1) Mr.P.Keerthi

    2) Mr.S.Kumaraguru



    Work Shop at Anna University

    Two students were selected through a

    Quiz competition related to heating

    ventilation and Air conditioning at ISHRAE

    Madurai Sub – Chapter. They were

    participated in one day work shop on Basic

    Air conditioning at Anna University, Chennai

    on 04.01.2014. The details of selected

    students are given below:

    Student Participation on Design

    competition of 9th

    Bry air Awards

    for HVAC Excellence

    Five students were participated 9th


    air Awards for excellence in HVAC & R

    2013-14 which was held at New Delhi on

    28.02.2014 with the title of solar energy

    based air-cooled telephone booth using peltier

    1) Mr.P.Keerthi

    2) Mr.N.Madhukrishnaa



    effect under the guidance of

    Dr.G.R.Kannan, Associate Professor,

    Department of Mechanical Engineering. The

    details of participants are as follows:

    1) Mr.S.Kumaraguru

    2) Mr.P.Keerthi

    3) Mr.K.Kirubakaran

    Student Articles

    1. History of Refrigeration- Mr.Milan Thapa, Secretary, Final Year

    Refrigeration may be defined as the process

    of achieving and maintaining a temperature

    below that of the surroundings, the aim

    being to cool some product or space to the

    required temperature. One of the most

    important applications of refrigeration has

    been the preservation of perishable food

    products by storing them at low

    temperatures. Refrigeration systems are also

    used extensively for providing thermal

    comfort to human beings by means of air

    conditioning. Air Conditioning refers to the

    treatment of air so as to simultaneously

    control its temperature, moisture content,

    cleanliness, odour and circulation, as

    required by occupants, a process, or products

    in the space. The subject of refrigeration

    and air conditioning has evolved out of

    human need for food and comfort, and its

    history dates back to centuries. The history

    of refrigeration is very interesting since

    every aspect of it, the availability of

    refrigerants, the prime movers and the

    developments in compressors and the

    methods of refrigeration all are a part of it.

    1.2. Natural Refrigeration

    In olden days refrigeration was

    achieved by natural means such as the use

    of ice or evaporative cooling. In earlier

    times, ice was either:

    1. Transported from colder regions,

    2. Harvested in winter and stored in ice

    houses for summer use or,

    3. Made during night by cooling of

    water by radiation to stratosphere.



    In Europe, America and Iran a

    number of icehouses were built to store ice.

    Materials like sawdust or wood shavings

    were used as insulating materials in these

    icehouses. Later on, cork was used as

    insulating material. Literature reveals that

    ice has always been available to aristocracy

    who could afford it. In India, the Mogul

    emperors were very fond of ice during the

    harsh summer in Delhi and Agra, and it

    appears that the ice used to be made by

    nocturnal cooling.

    1.2.1. Art of Ice making by Nocturnal


    The art of making ice by nocturnal

    cooling was perfected in India. In this method

    ice was made by keeping a thin layer of

    water in a shallow earthen tray, and then

    exposing the tray to the night sky.

    Compacted hay of about 0.3 m thickness was

    used as insulation. The water looses heat by

    radiation to the stratosphere, which is at

    around -55˚C and by early morning hours

    the water in the trays freezes to ice. This

    method of ice production was very popular in


    1.2.2. Evaporative Cooling

    As the name indicates, evaporative

    cooling is the process of reducing the

    temperature of a system by evaporation of

    water. Human beings perspire and

    dissipate their metabolic heat by

    evaporative cooling if the ambient

    temperature is more than skin

    temperature. Animals such as the

    hippopotamus and buffalo coat themselves

    with mud for evaporative cooling.

    Evaporative cooling has been used in India

    for centuries to obtain cold water in summer

    by storing the water in earthen pots. The

    water permeates through the pores of

    earthen vessel to its outer surface where it

    evaporates to the surrounding, absorbing its

    latent heat in part from the vessel, which

    cools the water. It is said that Patliputra

    University situated on the bank of river

    Ganges used to induce the evaporative-

    cooled air from the river. Suitably located

    chimneys in the rooms augmented the

    upward flow of warm air, which was

    replaced by cool air. Evaporative cooling

    by placing wet straw mats on the windows

    is also very common in India. The straw

    mat made from “khus” adds its inherent

    perfume also to the air. Now-a-days desert

    coolers are being used in hot and dry

    areas to provide cooling in summer.

    1.2.3. Cooling by Salt Solutions

    Certain substances such as common

    salt, when added to water dissolve in water

    and absorb its heat of solution from water

    (endothermic process). This reduces the

    temperature of the solution (water+salt).

    Sodium Chloride salt (NaCl) can yield

    temperatures up to -20˚C and Calcium

    Chloride (CaCl2) up to - 50˚C in properly

    insulated containers. However, as it is this

    process has limited application, as the

    dissolved salt has to be recovered from its

    solution by heating.

    1.3. Artificial Refrigeration

    Refrigeration as it is known these

    days is produced by artificial means.

    Though it is very difficult to make a clear

    demarcation between natural and artificial



    refrigeration, it is generally agreed that the

    history of artificial refrigeration began in

    the year 1755, when the Scottish professor

    William Cullen made the first refrigerating

    machine, which could produce a small

    quantity of ice in the laboratory. Based on

    the working principle, refrigeration systems

    can be classified as vapour compression

    systems, vapour absorption systems, gas

    cycle systems etc.

    1.3.1. Vapour Compression Refrigeration


    The basis of modern refrigeration

    is the ability of liquids to absorb

    enormous quantities of heat as they boil

    and evaporate. Professor William Cullen

    of the University of Edinburgh

    demonstrated this in 1755 by placing some

    water in thermal contact with ether under a

    receiver of a vacuum pump. The

    evaporation rate of ether increased due

    to the vacuum pump and water could be

    frozen. This process involves two

    thermodynamic concepts, the vapour

    pressure and the latent heat. A liquid is in

    thermal equilibrium with its own vapor at

    a pressure called the saturation pressure,

    which depends on the temperature alone.

    If the pressure is increased for example in a

    pressure cooker, the water boils at higher

    temperature. The second concept is that the

    evaporation of liquid requires latent heat

    during evaporation. If latent heat is

    extracted from the liquid, the liquid gets

    cooled. The temperature of ether will

    remain constant as long as the vacuum

    pump maintains a pressure equal to

    saturation pressure at the desired

    temperature. This requires the removal of

    all the vapors formed due to vaporization. If

    a lower temperature is desired, then a lower

    saturation pressure will have to be

    maintained by the vacuum pump. The

    component of the modern day refrigeration

    system where cooling is produced by this

    method is called evaporator.

    The refrigeration effect is obtained in

    the cold region as heat is extracted by the

    vaporization of refrigerant in the

    evaporator. The refrigerant vapour from

    the evaporator is compressed in the

    compressor to a high pressure at which its

    saturation temperature is greater than the

    ambient or any other heat sink. Hence when

    the high pressure, high temperature

    refrigerant flows through the condenser,

    condensation of the vapour into liquid takes

    place by heat rejection to the heat sink. To

    complete the cycle, the high pressure liquid

    is made to flow through an expansion valve.

    In the expansion valve the pressure and

    temperature of the refrigerant decrease. This

    low pressure and low temperature refrigerant

    vapour evaporates in the evaporator taking

    heat from the cold region.

    Fig 1. Vapour compression systems



    It should be observed that the system

    operates on a closed cycle. The system

    requires input in the form of mechanical

    work. It extracts heat from a cold space

    and rejects heat to a high temperature heat


    1.3.2. Vapour Absorption Refrigeration


    John Leslie in 1810 kept H2SO4

    and water in two separate jars connected

    together. H2SO4 has very high affinity

    for water. It absorbs water vapour and

    this becomes the principle of removing the

    evaporated water vapour requiring no

    compressor or pump. H2SO4 is an

    absorbent in this system that has to be

    recycled by heating to get rid of the

    absorbed water vapour, for continuous

    operation. Windhausen in 1878 used

    this principle for absorption refrigeration

    system, which worked on H2SO4.

    Ferdinand Carre invented aqua- ammonia

    absorption system in 1860. Water is a

    strong absorbent of NH3. If NH3 is kept in

    a vessel that is exposed to another vessel

    containing water, the strong absorption

    potential of water will cause evaporation of

    NH3 requiring no compressor to drive the

    vapours. A liquid pump is used to increase

    the pressure of strong solution. The strong

    solution is then heated in a generator and

    passed through a rectification column to

    separate the water from ammonia. The

    ammonia vapour is then condensed and

    recycled. The pump power is negligible

    hence; the system runs virtually on low-

    grade energy used for heating the strong

    solution to separate the water from

    ammonia. These systems were initially run

    on steam. Later on oil and natural gas based

    systems were introduced. Figure 1.4 shows

    the essential components of a vapour

    absorption refrigeration system. In 1922,

    Balzar von Platen and Carl Munters, two

    students at Royal Institute of Technology,

    Stockholm invented a three fluid system

    that did not require a pump. A heating

    based bubble pump was used for circulation

    of strong and weak solutions and hydrogen

    was used as a non-condensable gas to

    reduce the partial pressure of NH3 in the

    evaporator. Geppert in 1899 gave this

    original idea but he was not successful since

    he was using air as non-condensable gas.

    The Platen-Munters refrigeration systems

    are still widely used in certain niche

    applications such as hotel rooms etc. Figure

    2 shows the schematic of the triple fluid

    vapour absorption refrigeration system.

    Another variation of vapour

    absorption system is the one based on

    Lithium Bromide (LiBr)-water. This system

    is used for chilled water air-conditioning

    system. This is a descendent of

    Windhausen’s machine with LiBr replacing

    H2SO4. In this system LiBr is the absorbent

    and water is the refrigerant. This system

    works at vacuum pressures. The

    condenser and the generator are housed in

    one cylindrical vessel and the evaporator

    and the absorber are housed in second

    vessel. This also runs on low-grade energy

    requiring a boiler or process steam.



    Fig.2. Schematic of a triple fluid vapour

    absorption refrigeration system


    1. History of Refrigeration, IIT


    Student Article: 2

    Role of Engineers in Air conditioning


    Mr.P.Keerthi, Final Year

    Air-conditioning is a process that

    simultaneously conditions air; distributes it

    combined with the outdoor air to the

    conditioned space; and at the same time

    controls and maintains the required space’s

    temperature, humidity, air movement, air

    cleanliness, sound level, and pressure

    differential within predetermined limits for

    the health and comfort of the occupants, for

    product processing, or both. The acronym

    HVAC&R stands for heating, ventilating,

    air-conditioning, and refrigerating. The

    combination of these processes is

    equivalent to the functions performed by


    An air-conditioning or HVAC&R

    system consists of components and

    equipment arranged in sequential order to

    heat or cool, humidify or dehumidify, clean

    and purify, attenuate objectionable

    equipment noise, transport the conditioned

    outdoor air and recirculate air to the

    conditioned space, and control and maintain

    an indoor or enclosed environment at

    optimum energy use. The types of buildings

    which the air-conditioning system serves

    can be classified as:

    • Institutional buildings, such as

    hospitals and nursing homes

    • Commercial buildings, such as

    offices, stores, and shopping centers

    • Residential buildings, including

    single-family and multifamily low-rise

    buildings of three or fewer stories above


    • Manufacturing and storing


    1.1.Air-Conditioning Project Development

    and System Design

    The goal of an air-

    conditioning/HVAC&R system is to provide

    a healthy and comfortable indoor

    environment with acceptable indoor air



    quality, while being energy efficient and cost


    ASHRAE Standard 62-1989 defines

    acceptable indoor air quality as “air in which

    there are no known contaminants at harmful

    concentrations as determined by cognizant

    authorities and with which a substantial

    majority (80% or more) of the people

    exposed do not express dissatisfaction.” The

    basic steps in the development and use of an

    air-conditioning project are design,

    installation, commissioning, operation, and

    maintenance. There are two types of air-

    conditioning projects: designbid and design-

    build. A design-bid project separates the

    design (engineering consultant) and

    installation (contractors) responsibilities. In a

    design-build project, the design is also done

    by the installation contractor.

    1.2 Mechanical Engineer’s Responsibilities

    The normal procedure in a design-bid

    construction project and the mechanical

    engineer’s responsibilities are

    1. Initiation of a project by owner or


    2. Organizing a design team

    3. Determining the design criteria and

    indoor environmental parameters

    4. Calculation of cooling and heating


    5. Selection of systems, subsystems,

    and their components

    6. Preparation of schematic layouts;

    sizing of piping and ductwork

    7.Preparation of contract documents:

    drawings and specifications

    8. Competitive biddings by various

    contractors; evaluation of bids; negotiations

    and modifications

    9. Advice on awarding of contract

    10. Monitoring, supervision, and

    inspection of installation; reviewing shop


    11. Supervision of commissioning

    12. Modification of drawings to the

    as-built condition; preparation of the

    operation and maintenance manual

    13. Handing over to the property

    management for operation


    1. Wang, S.K. and Lavan, Z. “Air-

    Conditioning and Refrigeration”

    Mechanical Engineering Handbook Ed.

    Frank Kreith Boca Raton: CRC Press

    LLC, 1999.

    Student Article: 3

    Heating, Ventilation Air conditioning

    Mr.S.Kumaraguru, Final Year

    One of the most important decisions

    regarding a new home is the type of heating

    and cooling system to install. Equally critical

    is the heating and cooling contractor

    selected, as the operating efficiency of a

    system depends as much on proper

    installation as it does on the performance


    Keys to obtaining the design

    efficiency of a system in the field include:

    • Sizing and selecting the system for the

    heating, cooling, and dehumidification load

    of the home being built

    • Correct design of the ductwork or piping

    • Proper installation and charging of the

    HVAC unit

    • Insulating and sealing all ductwork or




    1.1 Types of HVAC Systems

    There are two primary types of central

    heating systems - forced-air systems and

    radiant heating systems. Most new homes

    have forced-air heating and cooling systems -

    either using a central furnace and air

    conditioner or a heat pump.

    Figure 1 shows that in forced-air systems

    a series of ducts distribute the conditioned

    heated or cooled air throughout the home.

    The conditioned air is forced through the

    ducts by a blower, located in a unit called an

    air handler. Most homes have three choices

    for central, forced-air systems: electric

    resistance heat or fuel-fired furnaces with

    electric air conditioning units or electric heat

    pumps, which can be either air-source or

    ground-source (geothermal). The best system

    for each home depends on many factors -

    cost, comfort, efficiency, annual energy use,

    availability, and local prices for fuels and


    When considering a HVAC system for a

    residence, remember that energy efficient

    homes have less demand for heating and

    cooling, so substantial cost savings may be

    obtained by installing smaller units that are

    properly sized to meet the load. Because

    energy bills in more efficient homes are

    Return Plenum Filter should be in a

    convenient location Refrigerant Lines

    Heating Source Blower Supply Plenum

    Branch Duct Trunk Duct Evaporation Coil

    Condensate Line 124 lower, higher

    efficiency systems will not provide as much

    annual savings on energy bills and may not

    be as cost effective as in less efficient


    1.2 Multiple HVAC Zones

    Larger homes often use two or more

    separate heating and air conditioning units

    for different floors or areas. Multiple

    systems can maintain greater comfort

    throughout the house while saving energy

    by allowing different zones of the house to

    be at different temperatures. The greatest

    savings come when a unit serving an

    unoccupied zone can be turned off.

    Rather than install two separate

    systems, HVAC contractors can provide

    automatic zoning systems that operate with

    one system. The ductwork in these

    systems typically has a series of

    thermostatically controlled dampers that

    regulate the flow of air to each zone.

    Although somewhat new in residential

    construction, thermostats, dampers, and

    controls for zoning large central systems

    have been used for years in commercial


    If your heating and air conditioning

    subcontractor feels that installing two or

    three separate HVAC units is needed,

    have them also estimate the cost of a

    single system with damper control over

    the ductwork. A single, larger system



    running longer is usually more efficient

    than separate systems.

    Such a system must be carefully

    designed to ensure that the blower is not

    damaged if dampers are closed to several

    supply ducts. In this situation, the blower

    still tries to deliver the same air flow as

    before, but now through only a few ducts.

    The reduced air flow creates back pressure

    against the blades of the blower and may

    cause damage to the motor. There are three

    primary design options:

    1. Create two zones and size the ductwork

    so that when the damper to one zone is

    closed, the blower will not suffer damage.

    The higher pressure can possibly damage the

    duct work as well, but that will not be

    noticed.2. Install a manufactured system that

    uses a dampered bypass duct connecting the

    supply plenum to the return ductwork. The

    control system always allows the same

    approximate volume of air to circulate.3.

    Use a variable speed HVAC system. Because

    variable speed systems are usually more

    efficient than single-speed systems, they will

    further increase savings.

    1.3 Air Conditioning Equipment

    Air conditioners and heat pumps work

    similarly to provide cooling and

    dehumidification. In the summer, they extract

    heat from inside the home and transfer it

    outside. In winter, a heat pump reverses this

    process and extracts heat from outside and

    transfers it inside. Both systems typically use

    a vapor compression cycle, which is

    described in Figures 3 and 4. This cycle

    circulates a refrigerant - a material that

    increases in temperature significantly when

    compressed and cools rapidly when

    expanded. The exterior portion of a typical air

    conditioner is called the condensing unit and

    houses the compressor, which uses most of

    the energy, and the condensing coil. The

    inside mechanical equipment, called the air

    handling unit, houses the evaporator coil, the

    indoor blower, and the expansion or throttling

    valve. The controls and ductwork for

    circulating cooled air to the house complete

    the system.



    1. Cold, liquid refrigerant circulates through

    evaporator coils. Inside air is blown across

    the coils and is cooled. This warms and

    evaporates the refrigerant. The cooled air is

    blown through the ductwork. The refrigerant,

    now a gas, flows to the outdoor unit.

    2. The compressor (in the outside unit)

    pressurizes the gaseous refrigerant. The

    refrigerant temperature rises, but remains a


    3. Fans in the outdoor unit blow air across the

    hot, pressurized gas in the condensing coil.

    The refrigerant cools and condenses into a


    4. The pressurized liquid flows inside to the

    air handling unit. It passes through an

    expansion valve, where its temperature drops

    as it vaporizes. The refrigerant flows to the

    evaporator coil and the process starts over.

    The exterior, air-cooled condensing

    unit should be kept free from plants and

    debris that might block the flow of air through

    the coil or damage the thin fins of the coil.

    Ideally, locate the condensing unit in the

    shade. However, do not block air flow to or

    from this unit with dense vegetation, fencing

    or overhead decking.

    1.4 Ventilation and Indoor Air Quality

    All houses need ventilation to

    remove stale interior air and excessive

    moisture. There has been considerable

    concern recently about how much

    ventilation is required to maintain the

    quality of air in homes. While there is

    substantial disagreement on the severity of

    indoor air quality problems, most experts

    agree that the solution is not to build an

    inefficient, “leaky” home. Because make-

    up air is brought in at outside

    temperatures, it often requires more

    energy to condition the home. However,

    the ventilation may reduce energy use by

    removing excess humidity. With humid

    environment, though, the outside air will

    typically be more humid than the inside


    Research studies show that

    standard houses are almost as likely to

    have indoor air quality problems as energy

    efficient ones. Most building researchers

    believe that no house is so leaky that the

    occupants can be relieved of concern about

    indoor air quality. They recommend

    mechanical ventilation systems for all


    The amount of ventilation required

    depends on the number of occupants and

    their lifestyle, as well as the design of the

    home. The ASHRAE standard,

    “Ventilation for Acceptable Indoor Air

    Quality” (ASHRAE 62) recommends that

    houses have 0.35 natural air changes per

    hour (nach) or 15 cubic feet per minute of

    ventilation per occupant.

    Older, drafty houses can have

    infiltration rates of 1.0 to 2.5 nach.



    Standard homes built today are tighter and

    usually have rates of from 0.5 to 1.0 nach.

    New, energy efficient homes often have

    less than 0.35 nach.

    Infiltration is not a successful means

    of ventilation because it is not reliable and the

    quantity of incoming air is not controllable.

    Air leaks are unpredictable, and infiltration

    rates for all houses vary. For example, air

    leakage is greater during cold, windy periods

    than during muggy, hot weather. Thus,

    pollutants may accumulate during periods of

    calm weather even in drafty houses. These

    homes will also have many days when

    excessive infiltration provides too much

    ventilation, causing discomfort, high energy

    bills, and possible deterioration of the

    building envelope.


    2. ASHRAE: American Society of Heating,

    Refrigerating and Air-Conditioning Engineers

    Student Article: 4

    Thermoelectric Refrigeration Systems

    Mr.K.Kirubakaran, Final Year

    A refrigeration effect can also be achieved

    without using any moving parts by simply

    passing a small current through a closed

    circuit made up of two dissimilar materials.

    This effect is called the Peltier effect, and a

    refrigerator that works on this principle is

    called a thermoelectric refrigerator.

    Fig 1. Working Principle

    In 1821 the German physicist T.J.

    Seebeck reported that when two junctions of

    dissimilar metals are kept at two different

    temperatures, an electro motive force (emf) is

    developed, resulting in flow of electric

    current. The emf produced is found to be

    proportional to temperature difference. In

    1834, a Frenchmen, J. Peltier observed the

    reverse effect, i.e., cooling and heating of two

    junctions of dissimilar materials when direct

    current is passed through them, the heat

    transfer rate being proportional to the current.

    In 1838, H.F.E. Lenz froze a drop of water by

    the Peltier effect using antimony and bismuth

    (it was later found that Lenz could freeze

    water as the materials used were not pure

    metals but had some impurities in them). In

    1857, William Thomson (Lord Kelvin)

    proved by thermodynamic analysis that

    Seebeck effect and Peltier effect are related

    and he discovered another effect called

    Thomson effect after his name. According to

    this when current flows through a conductor

    of a thermocouple that has an initial

    temperature gradient in it, then heat transfer

    rate per unit length is proportional to the

    product of current and the temperature. As the



    current flow through thermoelectric material

    it gets heated due to its electrical resistance.

    This is called the Joulean effect,

    further, conduction heat transfer from the hot

    junction to the cold junction transfers heat.

    Both these heat transfer rates have to be

    compensated by the Peltier Effect for some

    useful cooling to be produced.

    For a long time, thermoelectric

    cooling based on the Peltier effect remained

    a laboratory curiosity as the temperature

    difference that could be obtained using pure

    metals was too small to be of any practical

    use. Insulating materials give poor

    thermoelectric performance because of their

    small electrical conductivity while metals

    are not good because of their large thermal

    conductivity. However, with the discovery of

    semiconductor materials in 1949-50, the

    available temperature drop could be

    increased considerably, giving rise to

    commercialization of thermoelectric

    refrigeration systems.

    Fig. 2. Schematic of a thermoelectric

    refrigeration system

    Figure 2 shows the schematic of the

    thermoelectric refrigeration system based

    on semiconductor materials. The Russian

    scientist, A. F. Ioffe is one of the

    pioneers in the area of thermoelectric

    refrigeration systems using semiconductors.

    Several domestic refrigerators based on

    thermoelectric effect were made in USSR as

    early as 1949.

    However, since 1960s these systems

    are used mainly used for storing medicines,

    vaccines etc and in electronic cooling.

    Development also took place in many

    other countries. In USA domestic

    refrigerators, air conditioners, water coolers,

    air conditioned diving suits etc. were made

    using these effects.

    System capacities were typically

    small due to poor efficiency. However some

    large refrigeration capacity systems such as

    a 3000 kcal/h air conditioner and a 6 tonne

    capacity cold storage were also developed.

    By using multistage temperatures

    as low as 145oC were obtained. These

    systems due to their limited performance

    (limited by the materials) are now used only

    in certain niche applications such as

    electronic cooling, mobile coolers etc.

    Efforts have also been made to club

    thermoelectric systems with photovoltaic

    cells with a view to develop solar

    thermoelectric refrigerators.


    1. Refrigeration and Air Conditioning-IIT Kharagpur Notes



    Student Article: 5

    Current Trends in Low-Energy HVAC


    Mr. Milan Thapa, Secretary, Final Year

    Throughout the 20th century, trends

    in HVAC design have been determined

    largely by technological advances and energy

    costs. Engineers have always sought to find

    new ways to ensure occupant comfort, but

    the level of attention devoted to finding

    innovative ways to reduce energy use has

    fluctuated over the last few decades. When

    energy costs have risen, energy efficiency

    has become a priority; when they have been

    low, it has been less of a design driver. This

    article identifies several trends which are

    being used to reduce energy use in

    commercial buildings. The trends to be

    considered include decoupling of ventilation

    and heating/cooling, designing systems for

    optimal efficiency, increased analysis in

    system design, and total building integration.

    This article is not intended to be a technical

    argument or justification for selection of one

    system against another. Many technical

    articles are available for more complete

    handling of each of the trends.

    1.2 Decoupling of Ventilation and


    The current movement in HVAC design

    toward the decoupling of ventilation and

    heating is in some ways a return to the past.

    Prior to the widespread use of cooling for

    buildings, perimeter radiation of some form

    was typically used for heating, with operable

    windows providing ventilation.

    Following World War II, use of air

    conditioning became more common, mainly

    driven by prosperity and the manufacturing

    boom. Early air conditioning systems

    combined heating, ventilation, and air

    conditioning into a single system, delivered

    by the building’s central fan and air

    distribution network. This fan system

    typically delivered a mixture of outdoor air

    for ventilation along with warm or cool air to

    meet the building’s temperature requirements.

    Larger buildings would have separate systems

    or zones for interior and perimeter spaces.

    In more extreme climates, a perimeter

    heating system may also have been installed

    or reheat coils provided on ducts serving

    perimeter spaces. As prices soared during the

    energy crisis of the 1970s, engineers looked

    for a way to reduce costs and improve space

    comfort conditions. One solution, dual duct

    systems, provided warm air through one duct

    and cool air through another. The air would

    then be mixed at the zone level to provide

    appropriate temperature supply air for the

    zone’s needs, typically at constant volume.

    Dual duct systems allowed buildings to be

    divided into many more zones while using a

    larger central fan system. Dual duct systems

    also eliminated the need to re-heat air at the

    zone level resulting in less re-heat energy and

    reducing the piping network throughout the


    In one common example, a dedicated

    outside air system (DOAS), the airflow

    provided by the fan system is limited to the

    code-required ventilation component. The

    DOAS air handling unit provides heated and

    de-humidified air for ventilation and is

    frequently provided with some form of heat



    recovery component such as enthalpy transfer

    wheels, “run around” coils or heat pipes to

    further reduce energy consumption by

    utilizing building exhaust air to

    pre-condition the ventilation air.

    A DOAS system typically provides

    20% or less airflow than what would be

    provided at peak cooling periods utilizing a

    VAV system. With a DOAS system, the

    heating and cooling requirements for the

    space are met through a water-based system.

    Since water has a much higher capacity for

    energy transfer than air, the amount of

    energy required to deliver the heating and

    cooling is greatly reduced, while pump

    energy is somewhat increased.

    A side benefit of the reduced air

    quantity is smaller ductwork, which decreases

    the cost of the ventilation system and,

    potentially, the building’s required floor-to-

    floor height. DOAS systems are typically

    paired with passive chilled beams, radiant

    heating/cooling, or fan coils.

    When applying DOAS and chilled

    beam systems (shown in Figure 1), the

    designer must be careful to pay attention to

    how the air is distributed to the space and

    how heating is accomplished. In buildings

    with low heating needs, the ventilation air

    may be able to provide adequate heating. In

    buildings with higher heating requirements,

    supplemental heating systems such as

    perimeter baseboard may be required. It is

    critical that the ventilation air reach the

    occupied breathing zone. For this reason,

    DOAS systems are frequently configured to

    deliver the air with a displacement strategy at

    low level.

    Fig. 1. Passive chilled beam system diagram

    Fig 2. Active chilled beam diagram.

    A second type of decoupled system

    could be considered a hybrid model. Active

    chilled beams (shown in Figure 2) deliver

    both ventilation and heating/cooling services,

    but induced air at the chilled beam delivers

    most of the heating and cooling while the air

    handling unit provides only a portion of the

    requirements. The primary airflow for an

    active chilled beam system is more than that

    of a DOAS/passive chilled beam system

    because the active chilled beam utilizes the

    primary air to induce room air across the coil



    in the beam. The static pressure in the

    primary air system may also be higher than

    that of a DOAS system. Similar to the

    DOAS/passive chilled beam system,.

    We analyzed a simple 20-story

    building to compare the DOAS/passive

    chilled beam system and the active chilled

    beam system to an ASHRAE standard 90.1

    baseline VAV system. The results of the

    study are reflected in Figure 3.

    Fig 3: Fan energy comparison

    The pictures of low energy HVAC

    design are given for easy understanding


    1. Robert l. Tazelaar, Pe, Leed Ap,Current

    trends in hvac design –National Science

    Foundation work shop, 2013.

  • Volume: 01-Issue: 01, August 2014


    Department of Mechanical Engineering, PSNA College of Engineering and Technology

    Kothandaraman Nagar, Dindigul -624622, Tamil Nadu,

    ISHRAE Cover page model 28 10 2015.pdfFront page 2013-August 14.pdfInauguration of ISHRAE 2013-14.pdfISHRAE Cover end page 28 10 2015.pdf