HVAC System DesignPES Institute of Technology

ObjectiveGoal: To develop an automotive air-conditioning system that is smaller and lighter than with conventional technology.

The Challenge: The system must be capable of keeping a temperature of 22C inside a stationary black vehicle with four occupants, with an outside temperature of 40C. Also, the system must be an efficient heating system, keeping an internal temperature of 15C with an outside temperature of 0C.

H.V.A.CH.V.A.C Heating, Ventilation and Air Conditioning system

The HVAC regulates:Room TemperatureHumidityAir QualityAir Flow

Refrigeration CycleVapour Compression Cycle

Design Parameters & ConsiderationsHeat Load on the HVAC = 5.287 kWCabin Relative Humidity = 40%Evaporator Temperature = 4CRefrigerant Used= R134aRefrigeration Cycle : Vapour Compression

Cabin design cooling and heating requirementsTemperature and Humidity rangePlacement of Vents and DuctsSpace considerationsEffect on car performanceEfficiencyEnvironmental Impact

Cycle Analysis & Heat LoadAssumptions:Compression process is isentropic.No pressure losses in piping.Condenser temperature = 46C.Evaporator Temperature = 4 C.Refrigerant is not sub cooled.

Heat Load Calculations:Heat due to opaque surfaces = 3598.2 WHeat due to fenestration = 1229.66 WInternal Loads ( human ) = 460 W

Total Load = 5.287 kW

ResultsEvaporator Pressure = 3.38 barCondenser Pressure = 11.9 barHeat Load = 5.287 KWCondenser Cooling Load= 6.308 KWCompressor Work = 1.02 KWMass Flow Rate = 1.94 l/min

Selection BasisScroll Compressors Compact design and High Volumetric Efficiency ( around 98% ).Refrigerant R134a Minimized environmental impact.Plate-Fin Heat Exchanger-Compact size, Higher heat transfer capability.Simple design incorporated to minimize cost.

Heart of the system, belt driven pump that fastened to engine.Responsible for compressing and transferring refrigerant.

Two interleaved scrolls with involute geometry.One scroll fixed while the other orbits eccentrically to compress fluidAdvantage:Very high volumetric efficiency (almost 98%)Lesser Noise and lighter compared to rotary compressor.Compressor

Responsible for heat dissipation The condenser is designed to radiate heat. Located in front of the radiator Require good air flow when system is in operation Plate fin type heat exchanger with micro channels used.Very compact and better heat transfer capability.Hot compressed refrigerant vapour cools at constant pressure to liquid.

Overall Heat Transfer Coefficient = 92 W/m2KArea = 6.87 m2Condenser

Depending on the vehicle, the A/C system will either have a receiver dryer or an accumulator.Components contain a desiccant, chemical that attracts moisture.Prevents formation of corrosive acids on mixture of water and acid.Also act as temporary storage for refrigerant to prevent starving of evaporatorAccumulator

Heat absorption component.Used remove heat from the inside of vehicle. Secondary benefit - dehumidification. Unconditioned air passes through a filter before entering the evaporator.Plate-fin evaporator with micro channels used.

Overall heat transfer coefficient = 98 W/m2KArea calculated = 3.04 m2Fan Flow Rate = 90 l/s Evaporator

Layout of Components

Looking AheadFinalize and validate results based on inputs from other teams.Improvise on the current design and form a cost effective solution.Documentation and reports.

Thank You !