Day 1- What is HVAC

7/28/2019 Day 1- What is HVAC

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What is HVAC ?HVAC Heating, Ventilation and Air-Conditioning.

Heating The temperature out side is less than inside.

Ventilation Sending the air out from the space and/or supplying the fresh air into the space.

Air-Conditioning It mean a process by which the temperature,humidity, flow and purity of the air is controlledsimultaneously to get the required conditions.


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Why do we require air

conditioning?

To improve or control an Industrial process.To maintain Human comfort.


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Man a heat Machine

Food eaten is the fuel.Every body movement generates heat eventhe blink of an eye.To maintain 98.6 Degrees Fahrenheit itrejects heat.what are modes of Heat Transfer?


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Heat Transfer

ConductionConvectionRadiation


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Conduction : The heat transfer due to conductiontakes place if the two bodies at differenttemperatures are in contact with each other. It is

also true if a substance is heated from one end.heat transfer takes place to the other end byconduction.Convection : When liquid or gas is heated,

expansion takes place. Due to this it becomeslighter and rises up. Its place is taken by colder or dense fluid. This is a continuous process and thusheat transfer takes place due to these currents and

heat is distributed through the mass. Radiation : The heat transfer due to radiationtakes place from one body to another withouteffecting the medium through which heat travels.

Heat flow from sun to earth takes place in thisfashion.


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Human beings are rejecting heat byConvection, Radiation and Evaporation.All three methods normally are used at thesame time.All three methods gives off excess heat.One method may do more and the other may do less.

Depending on the surrounding conditions.


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What are the surrounding

conditions ?TemperatureRelative HumidityAir Motion

Change in each of this surroundingcondition will speed up or slow down theheat rejection or gain.


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Comfort Zone for Human

beings.What is the best temperature in which allwill feel comfort ?

What is the best relative humidity whichgives you comfort ?Temperature Range 22-26.5 CRelative Humidity 30-70% .


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Outside and Inside

A man in out door needs to adjust him self with his clothing and whims of nature.

A man inside shelter We can control hiscomfort.HOW ?


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By means of HVAC

Openings in the field of HVACMarketingDesignInstallation

Commissioning and TestingMaintenanceOutsourcing


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Fundamentals

Heat Q is the mechanism that transfersenergy across the boundaries of

systems with differing temperatures,always toward the lower temperature.


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Sensible heat factor :

The sensible heat factor is theratio of sensible heat to the

total heat. The total heat of air is the sum of sensible heat andlatent heat.

SHF = SH/TH


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Sensible Heat : It is defined as the amount of heat

required to raise the temperature of 1kg of substance from 0 C to the desired temperaturewithout changing its state.Latent Heat : Latent heat of a substance variesfrom its sensible heat as it does not cause anytemperature variation within the body but changesits state i.e.., from solid to liquid or liquid to gas.

Example : 80 Kcal of heat is absorbed from thesurroundings when 1kg of ice changes into water at a constant temperature 0 C to freeze it to ice atthe same temperature.


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Units of Refrigeration

The unit of refrigeration is termed asTons of refrigeration or simply Tons

and it is equal to the amount of heatrequired to enable 1 ton of ice to melt in24 hours.

In MKS system 1Ton = 3,000 k cal/hour or 50k cal/min.In British Units 1 Ton = 12,000 BTU/hr.

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Day 1- What is HVAC