www.hvacdesigning.com presents - automotive hvac generic presentation

8/3/2019 Www.hvacdesigning.com Presents - Automotive HVAC Generic Presentation

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MOBILE AIR CONDITIONINGBasic A/C Operation


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Need for Air Conditioning

Ventilation, heating, and air conditioning provide for thecomfort of the vehicles passengers.

The ventilation system on most vehicles is designed tosupply outside air to the passenger compartment through

upper or lower vents or both.

Heat interactions between vehicle & outer environment


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Basic Air Conditioning Cycle

All systems contain six major components:

Compressor to circulate the refrigerant

Condenser to transfer heat to ambient air

Receiver dryer or accumulator to store reserve refrigerant, contain the

desiccant, and filter refrigerant

Expansion device to control amount of refrigerant entering evaporator

Evaporator to transfer heat from in-vehicle air to the refrigerant

Lines and hoses to connect these parts together

And the refrigerant

A Typical air conditioning cycle


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36 KW Split Kit & Bus Layout

A Typical automotive air conditioner

A Typical car air conditioner

A Typical bus air conditioner


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Typical Air flow in a typical automotive HVAC

Fire wall

Blower

Evaporator

Thermister

Heater

A Typical Air flow diagram in a typical automotive HVAC


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R12

y Chloro Fluoro Carbon (CFC)

y Ozone Depletion

y

Global Warming Potential(GWP)y ND 6 Compressor oil (Mineral Oil)

y O Ring material - NBR

y UNF THREADS AT THE JOINTS

R134a

y Hydro Fluoro Carbon (HFC)

y ZEROOzone Depletion

y

GWP -lessery ND 8 Poly alkaline Glycol (PAG)

y O Ring material - RBR

y METRIC THREADS

Common Refrigerantsused in automotive air conditioners

A comparative study between refrigerants


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1. Mounted on the engine

2. Is belt driven

3. Has a magnetic clutch in front

4. Pumps refrigerant in a closed loop throughthe system

5. Takes in low pressure gas from the

evaporator and compresses this to a highpressure super heated gas

Introduction to automotive compressors

1. The compressor separates the high-pressure and low-

pressure sides of the system.2. The primary purpose of the unit is to draw the low-

pressure and low-temperature vapour from the

evaporator and compress this vapour into high-

temperature, high-pressure vapour.

3. The secondary purpose of the compressor is to

circulate or pump the refrigerant through the A/C

system under the different pressures required for

proper operation.

Classification of automotive compressors

Crank type

Swash type

Wobble type

Reciprocating

type

Rotarytype

Vane type

Wankle type

Screw type

Scroll type

Out/Discharge: High Pressure, about 200

psi & High Temperature, above ambient

In/Suction: Low Pressure, about30 psi & Low Temperature, close to

freezing


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Scroll Compressor Classification ofautomotive compressors

Scroll compressor

The orbiting scroll is driven by the crankshaft and moves in a

small circular orbit. The fixed scroll remains stationary


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Classification ofautomotive compressors

The wobble plate does not rotate; it just wobbles, being drivenby the angled drive plate that does rotate. Variabledisplacement, wobble plate compressors can change the angleof the drive plate, and this changes piston stroke and

compressor displacement. Most wobble plate compressors have5 to 7 pistons.

Wobble Plate Compressors

The swash plate is mounted at an angle onto the drive shaft . Itdrives three double-ended pistons. Two sets of reeds control the

refrigerant flow in and out of the cylinders,

Swash Plate Compressors

The rotor is driven by the clutch and driveshaft. The vanes move inand out of the rotor to follow the outer wall to pump refrigerant.Vane Compressors

Scotch Yoke Compressors A Scotch yoke compressor has two pairs of pistons that aredriven by a slider b lock on the crankshaft. The pistons are

connected by a yoke.

Provide smooth compressor operation

Maintain constant evaporator temperature

Reduces compressor load on engine when

system cooling load is low

Benefits of Variable Displacement Compressors


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Evaporator Operation

1. Evaporator

1. The evaporator consists of a refrigerant coil mounted in a series of thin cooling fins.

2. The evaporator is usually located beneath the dashboard or instrument panel.

3. On receiving the low-pressure, low-temperature liquid refrigerant from the thermostatic expansion valve or orifice

tube in the form of an atomized (or droplet) spray, the evaporator serves as a boiler or vaporizer to boil therefrigerant.

4. Heat from the core surface is lost to the boiling and vaporizing refrigerant, which is cooler than the core, thereby

cooling the core.

5. Air passing over the evaporator loses its heat to the cooler core, thereby cooling the air inside the car.

6. Any moisture (humidity) in the air passing over the core condenses on the outside and is drained off as water.

Introduction to automotive evaporators


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SP Evaporator

(SERPENTINE)

SBR, ZEN,

INDICA,

Toyota Quails.

ST Evaporator

(SINGLE TANK MULTIFLOW )

ESTEEM

MS Evaporator

(MULTITANK MULTIFLOW SUPERSLIM)

LATEST

RS Evaporator

Classification ofautomotive evaporators


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Condenser Assembly

In front of the radiator

Removes the heat from the refrigerant

It takes in hot high pressure gas and cools it.

The gas goes changes to a sub cooled liquid as it cools.

The output of the condenser is at the bottom.

Air Center Tube Reinforcement

Outlet Tube

& Fitting

Inlet Tube& Fitting

Mounting Bracket

Transition Fitting

A Serpentine Tube-and-Center (STC) Condenser

Introduction to automotive condensers

Hot, high pressure gas is pumped from the

compressor to enter the condenser.The gas gives up its heat to the

air passing through the condenser. Removing

heat from the hot gas causes it to change state

and become liquid.

Condenser Operation


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Classification ofautomotive condensers

Condensers A and C are round tube, serpentinecondensers.

Condenser B is an oval/flat tube, serpentine condenser.

Condenser D is an oval/flat tube, parallel flowcondenser.

Flat tube condensers are more efficient.

Condenser Types

Refrigerant flows from the upper inletto the bottom outlet through two tubes.These tubes wind back and forth

though the condenser.

Serpentine Condenser

Refrigerant flows from the upper inlet to the bottom outletthrough groups of parallel tubes. Some carry refrigerant fromthe right to the left, and others move it back to the right side.

Parallel Flow Condenser


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Methods ofautomotive cabin heating

(1) By utilizing the heat of engine coolant using a heat exchanger

(2) By reverse operation of Air conditioning cycle using it as a heat pump

(3) By using the reverse thermo electric air conditioners (Based on Peltier Effect)

(4) By using the electric Heaters (PTC heaters)

(7) By using fuel f ired heater

(5) By using heated Windshield

(6) By using the infrared lamps

(8) By using seat Heaters

Use Infrared light bulbs to heat a person's body

A special windshield has fine wires to electrically defrost.

These heaters use kerosene or gasoline as fuel to generate heat. Units are available in marketwhich fit drop in with the existing heater core systems. Although these units use fossil fuel, they put

out a lot of heat, which can be useful in very cold climates.

The following methods are widely used for automotive cabin heating:-


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Layout ofautomotive heaters

HVAC componentsLay out

Heater core lay out position in an automotive HVAC


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Component circuit ofautomotive heaters

HEATING SYSTEM COMPONENTS:-

Heater control valve

Heater core

Blower motor and fan

Blower motor electrical controls

Heater and defroster ducts

Mode door controls

Lever Assy

Plastic Cases

Heater core

Blower motor assemblyDoor assembly

Plastic casesLever assembly

Heater Control Panel:-

Manual Control Type Automatic Control Type

Heater Control cable Automatic Control cable

Manual Control Type

Automatic Control Type


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Air Flow circuit of Automotive heaters

Section View

Block diagram of HVAC air flow:-

Typical air flow patterns of an automotive HVAC:-


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The expansion device separates the high side from the low side and

provides a restriction for the compressor to pump against.

There are two styles of expansion devices:

The TXV can open or close to change flow . It is controlled by the

superheat spring, thermal bulb that senses evaporator outlet

temperature, and evaporator pressure

Most OTs have a fixed diameter orifice

Expansion Devices

The three major types of expansion valves:

Internally balanced TXVs are the most common.

Externally balanced TXVs are used on some larger evaporators.

Block valves route the refrigerant leaving the evaporator past the

thermal sensing diaphragm so a thermal bulb is not needed.

InternallyBalanced

ExternallyBalanced

Block Valve

Introduction to automotive expansion devices


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19

The OT used in a modern vehicle is a tubular, plastic device with a small metal tube

inside. The color of the OT is used to determine the diameter of the tube. A plastic filter

screen is used to trap debris that might plug the tube.

Some older General Motors vehicles used an OT that resembled a brass fuel filter.

Fixed orifice tube

Orifice tubes

Orifice Tubes


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Accumulators are used in the suction line of all OT systems.

The accumulator:

separates liquid refrigerant so only gas flows to the compressor.

Allows oil in the bottom of the accumulator to return to the

compressor.

provides storage for a refrigerant reserve.

contains the desiccant bag for water removal.

provides a place to mount low pressure switches and sensors.

Accumulators

Accumulators


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A receiver dryer is mounted in the liquid

line of a TXV system. It is used to:

to store a reserve of refrigerant.

hold the desiccant bag that removes water

from the refrigerant.

filter the refrigerant and remove debris

particles.

provide a sight glass so refrigerant flow can

be observed.

provide a location for switch mounting.

Receiver Drier


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Low Refrigerant Levels:y Allow refrigerant to vaporize before evaporator

y Prevent proper heat transfer in evaporator

y Causes low system pressures

High Refrigerant Levels:

y Prevent refrigerant expansion in evaporator

y Can cause extremely high system pressures

y Prevents heat transfer because of high pressure in

evaporator

Effect of refrigerant charge levels


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Controlsand safety devices

Thermostat

Dampers

Dual pressure switch Pressure relief valve

CONTROLS & SAFETYDEVICES

A/C systems can include a pressure release valve that is usually mounted at the compressor or a fuse plug mounted on the receiver dryer.

The relief valve can open at a preset pressure and then reclose. The center of the fuse plug melts to let pressure escape.


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HOSE ASSEMBLY

Hose suction

Low Pressure

y Three layers (EPDM, Polyester,Intermediate rubber)

y Cooling unit to Compressor

Hose Discharge

High Pressure

y Four Layers (Nylon Layer inside to minimize permeability)

y Compressor to Condenser

Hose assembly


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Tube Suction

y 5/8 Tube CarriesLow pressurevapor.

y Connects Cooling Unit and Hose

suction.

Tube Discharge

y Tube carries compressed super heated

Vapor.

y Connects Hose discharge and

Condenser

Tube liquid

y 8mm Tube carries liquid refrigerant.

y Connects Condenser out, Receiver

Drier & TXV

y Receiver TO Cooling Unit

y Sight glass for checking

y Dual pressure switch

y Charging portA/c liquidline

A/c Orifice tube

Tubesand pipings


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Automatic HVAC

Automatic Climate Control


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Manufacturing InfrastructureManufacturing infrastructure required for HVAC manufacturing


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Product Development Infrastructure:R&D / Tool Room

Testing and validation


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