FAISAL....HVAC Assignment

7/31/2019 FAISAL....HVAC Assignment

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Submitted by:

Faisal Rafique

Topic:

Heat pump trainer

Subject:

HVAC

Roll#:

09-MC-76

3rd year, 6 th semester

Mechanical Engineering Department

NFC-IEFR, Faisalabad


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Heat pump:

A heat pump is a device that extracts heat from one place and transfers it to

another.

Heat pumps transfer heat by circulating a substance called a refrigerant

through a cycle of evaporation and condensation. A compressor pumps the

refrigerant between two heat exchanger coils. In one coil, the refrigerant is

evaporated at low pressure and absorbs heat from its surroundings. The refrigerant

is then compressed en route to the other coil, where it condenses at high pressure.

At this point, it releases the heat it absorbed earlier in the cycle.


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Basic Refrigeration Cycle/Cooling cycle:

Refrigeration may be defined as the process of removing heat from a body or

enclosed space so that its temperature first lowered and maintain at a level belowthe temperature of the surroundings.

The system maintained at lower temperature is called refrigeration system

and equipment used to maintain this lower temperature is called refrigerant

equipment.

Refrigerant

A refrigerant is a substance used in a heat cycle usually including, for

enhanced efficiency, a reversible phase change from a liquid to a gas.

Traditionally, fluorocarbons, especially chlorofluorocarbons, were used as

refrigerants, but they are being phased out because of their ozone effects. Other

common refrigerants used in various applications are ammonia, sulfur dioxide, and

non-halogenated hydrocarbons such as methane

Principles of Refrigeration:

Liquids absorb heat when changed from liquid to gas

Gases give off heat when changed from gas to liquid.

For an air conditioning system to operate with economy, the refrigerant must be

used repeatedly. For this reason, all air conditioners use the same cycle of

compression, condensation, expansion, and evaporation in a closed circuit. The

same refrigerant is used to move the heat from one area, to cool this area, and to

expel this heat in another area.
http://en.wikipedia.org/wiki/Heat_enginehttp://en.wikipedia.org/wiki/Phase_changehttp://en.wikipedia.org/wiki/Liquidhttp://en.wikipedia.org/wiki/Gashttp://en.wikipedia.org/wiki/Organofluorine_chemistryhttp://en.wikipedia.org/wiki/Chlorofluorocarbonhttp://en.wikipedia.org/wiki/Ammoniahttp://en.wikipedia.org/wiki/Sulfur_dioxidehttp://en.wikipedia.org/wiki/Methanehttp://en.wikipedia.org/wiki/Methanehttp://en.wikipedia.org/wiki/Sulfur_dioxidehttp://en.wikipedia.org/wiki/Ammoniahttp://en.wikipedia.org/wiki/Chlorofluorocarbonhttp://en.wikipedia.org/wiki/Organofluorine_chemistryhttp://en.wikipedia.org/wiki/Gashttp://en.wikipedia.org/wiki/Liquidhttp://en.wikipedia.org/wiki/Phase_changehttp://en.wikipedia.org/wiki/Heat_engine


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The refrigerant comes into the compressor as a low-pressure gas, it is

compressed and then moves out of the compressor as a high-pressure gas.

The gas then flows to the condenser. Here the gas condenses to a liquid, andgives off its heat to the outside air.

The liquid then moves to the expansion valve under high pressure. This

valve restricts the flow of the fluid, and lowers its pressure as it leaves the

expansion valve.

The low-pressure liquid then moves to the evaporator, where heat from the

inside air is absorbed and changes it from a liquid to a gas.

As a hot low-pressure gas, the refrigerant moves to the compressor wherethe entire cycle is repeated.


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Heating Cycle:

During the heating cycle, heat is taken from outdoor air and "pumped"indoors.

First, the liquid refrigerant passes through the expansion device, changing to

a low-pressure liquid/vapour mixture. It then goes to the outdoor coil, which

acts as the evaporator coil. The liquid refrigerant absorbs heat from the

outdoor air and boils, becoming low-temperature vapours.

These vapours pass through the reversing valve to the accumulator, which

collects any remaining liquid before the vapours enter the compressor. The

vapours are then compressed, reducing its volume and causing it to heat up.

Finally, the reversing valve sends the gas, which is now hot, to the indoor

coil, which is the condenser. The heat from the hot gas is transferred to the

indoor air, causing the refrigerant to condense into a liquid. This liquid

returns to the expansion device and the cycle is repeated. The indoor coil is

located in the ductwork, close to the furnace.


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Components of heat pump:

Compressor:

The purpose of the compressor is to circulate the refrigerant in the system

under pressure; this concentrates the heat it contains.

At the compressor, the low pressure gas is changed to high pressure gas.

Condenser:

The purpose of the condenser is to receive the high-pressure gas from the

compressor and convert this gas to a liquid .

It does it by heat transfer, or the principle that heat will always move from a

warmer to a cooler substance.

Air passing over the condenser coils carries off the heat and the gas

condenses.


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Expansion Valve:

A thermal expansion valve is a component in refrigeration and air

conditioning systems that controls the amount of refrigerant flow into the

evaporator thereby controlling the superheating at the outlet of the evaporator.

The expansion valve removes pressure from the liquid refrigerant to allow

expansion or change of state from a liquid to a vapor in the evaporator.

Evaporator:

The evaporator works the opposite of the condenser; here refrigerant liquid

is converted to gas, absorbing heat from the air in the compartment. When the

liquid refrigerant reaches the evaporator its pressure has been reduced, dissipating

its heat content and making it much cooler than the fan air flowing around it.
http://en.wikipedia.org/wiki/Refrigerationhttp://en.wikipedia.org/wiki/Air_conditioninghttp://en.wikipedia.org/wiki/Air_conditioninghttp://en.wikipedia.org/wiki/Superheatinghttp://en.wikipedia.org/wiki/Evaporatorhttp://en.wikipedia.org/wiki/Evaporatorhttp://en.wikipedia.org/wiki/Superheatinghttp://en.wikipedia.org/wiki/Air_conditioninghttp://en.wikipedia.org/wiki/Air_conditioninghttp://en.wikipedia.org/wiki/Refrigeration


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Thermostat:

A thermostat is a component of a control system which senses thetemperature of a system so that the system's temperature is maintained near a

desired set point.

Pressure gauge:

Pressure gauges are devices used for measuring the pressure of a gas orliquid.

High Pressure Control:

A pressure operated control which opens an electrical circuit if high sidepressure becomes too high.


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Capillary tube:

A capillary tube is a refrigerant control; its common types of air conditioner

expansion valve. The capillary is simply a length of tubing with a small inside

diameter which acts as a constant throttle on the refrigerant entering the

evaporator.

Needle valve:

A needle valve is a type of valve having a small port and a threaded, needle-

shaped plunger. It allows precise regulation of flow, although it is generally only

capable of relatively low flow rates.
http://en.wikipedia.org/wiki/Valvehttp://en.wikipedia.org/wiki/Screw_threadhttp://en.wiktionary.org/wiki/precisionhttp://en.wikipedia.org/wiki/Fluid_dynamicshttp://en.wikipedia.org/wiki/Fluid_dynamicshttp://en.wiktionary.org/wiki/precisionhttp://en.wikipedia.org/wiki/Screw_threadhttp://en.wikipedia.org/wiki/Valve


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Check valve:

A check valve, clack valve, non-return valve or one-way valve is

a mechanical device, a valve, which normally allows fluid (liquid or gas) to flow

through it in only one direction.

Pressure transducer:

A pressure transducer is a type of pressure sensor that measures pressure,

typically of gases or liquids. Pressure sensors can also be used to indirectly

measure other variables such as fluid/gas flow, speed, water level, and altitude.
http://en.wikipedia.org/wiki/Mechanical_devicehttp://en.wikipedia.org/wiki/Valvehttp://en.wikipedia.org/wiki/Fluidhttp://en.wikipedia.org/wiki/Liquidhttp://en.wikipedia.org/wiki/Gashttp://en.wikipedia.org/wiki/Pressurehttp://en.wikipedia.org/wiki/Gashttp://en.wikipedia.org/wiki/Gashttp://en.wikipedia.org/wiki/Pressurehttp://en.wikipedia.org/wiki/Gashttp://en.wikipedia.org/wiki/Liquidhttp://en.wikipedia.org/wiki/Fluidhttp://en.wikipedia.org/wiki/Valvehttp://en.wikipedia.org/wiki/Mechanical_device


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Manual valves:

Manual valves are those valves that operate through a manual operator (such

as a hand wheel or hand lever), which are primarily used to stop and start flow

(block or on off valves), although some designs can be used for basic throttling.

Sight glass:

A sight glass or water gauge is a transparent tube through which the operator

of a tank or boiler can observe the level of liquid contained within.


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Flow meter:

A flow meter is an instrument used to measure linear, nonlinear, mass or

volumetric flow rate of a liquid or a gas.

Air flow meter:

An air flow meter is a device that measures air flow, i.e. how much air is

flowing through a tube. It does not measure the volume of the air passing through

the tube; it measures the actual speed of the air flowing through the device in adefined time segment.
http://en.wikipedia.org/wiki/Airflowhttp://en.wikipedia.org/wiki/Airhttp://en.wikipedia.org/wiki/Volumehttp://en.wikipedia.org/wiki/Volumehttp://en.wikipedia.org/wiki/Airhttp://en.wikipedia.org/wiki/Airflow


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Air flow sensor:

A device that's used in many electronic fuel injection systems for measuring

the volume of air entering the engine. Some use a spring-loaded vane while others

use a hot wire or heated filament to sense air flow.

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