01 Principles%20of%20Heating%20and%20Refrigeration, BMW educational info, Dokumentacja

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01 Principles%20of%20Heating%20and%20Refrigeration, BMW educational info, Dokumentacja

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//-->Table of ContentsPrinciples of Heating andRefrigerationSubjectPageHeating Ventilation Refrigeration (HVAC) . . . . . . . . . . . . . . . . . . . . . . .3Comfort in the Vehicle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4Heat is a Strain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5“The Comfort Zone” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6Principals of Heating and Refrigeration . . . . . . . . . . . . . . . . . . . . . . . . .7Heat and Cold Explained . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7Condensation and Evaporation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8Evaporation of Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8Heat Transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9Sensible and Latent Heat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10Types of Latent Heat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10Change of State . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11First Natural Law . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11Heat and Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12BTUs and Calories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12Effects of Pressure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16Pressure and Boiling Points . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18Boiling Point of Various Substances . . . . . . . . . . . . . . . . . . . . . . . . . . .19Initial Print Date: 10/07Revision Date:Principles of Heating and RefrigerationModel: AllProduction: AllAfter completion of this module you will be able to:• Describe the difference between a HVAC system and aClimate Control System.• Describe the meaning of the “Comfort Zone”.• Identify the principles of Heating and Refrigeration.2Principles of Heating and RefrigerationHeating Ventilation Refrigeration (HVAC)The purpose of the heating, ventilation and air conditioning system is to treat the airentering the passenger compartment in order to achieve and maintain a constantlycomfortable environment for the occupants.This is achieved by:• Heating or cooling the area depending on the requirements or demandsof the driver / passenger and dictated by outside temperatures.• Circulating air through out the vehicle.• Removing moisture, to assist in defogging of the windowsand enhancing occupant comfort level.• Filtering the air to remove dust, allergens.The modern automotive system that cools, heats, dehumidifies, ventilates and filters theair entering the passenger compartment is referred to asClimate Control.ClimateControl describes a more complete and precise management of the basic HVAC sys-tem, where the vehicles internal climate is constantly varied and adjusted depending onthe occupants desired and requested settings..Climate Control Sub-Systems:• Air Conditioning• Heater• Air Management (blower, filters, vents)• Computer ControlsNote: Scientific investigations conducted by the World Health Organizationshows that concentration and reaction diminish considerably under theeffects of stress and strain.3Principles of Heating and RefrigerationComfort in the VehicleHumans feel comfortable at a certain ambient temperature and atmospheric humidity.The feeling of well-being plays a significant part in ensuring the driver's comfort whiledriving. The "climate in the vehicle" has a direct influence on the driver fatigue and over-all safety.A comfortable interior temperature is determined by the prevailing outside temperature,solar radiation and adequate air output rate and circulation.• A low outside temperature of -20°C, requires a higher interior temperature of28°C and an air output rate of approx. 5-6 kg/min.• A high outside temperature of 40°C, requires a low interior temperature of23°C and an air output rate of approx. 10 kg/min.• A moderate outside temperature of 10°C, requires a low interior temperature of21.5°C and an air output rate of approx. 4 kg/min.Even modern heating and ventilation systems have difficulty achieving total comfort inthe vehicle interior at high outside temperatures.• Particularly under conditions of high solar radiation (strong sunshine), the heated airin the vehicle interior can be replaced only by air at ambient temperature.• Opening a window or sunroof or increasing the fan speed to achieve the feeling ofcomfort often involves draughts and other annoyances such as noise, exhaustfumes and pollen.Comfort CurveIndexABC12ExplanationInterior temperatureAir delivery (vent output)Outside temperatureComfort curve - air outputComfort curve - interior temperaturePhysical strain increases by a multiple at highhumidity levels.4Principles of Heating and RefrigerationEffects of unfavorable vehicle interior temperatures on peopleAreaHeadChestFeetWith air conditioning23°C (73°F)24°C (75°F)28°C (82°F)Without air conditioning42°C (107°F)40°C (104°F)35°C (95°F)Temperatures in a medium-class passenger car at: Driving time 1h, outside temperature30°C (86°F) and sun shining (solar radiation) on the car.Heat is a StrainThe ideal temperature for the driver is 20°C (69°F) to 22°C (72°F). This corresponds tothe comfort zone A with low climatic strain:• Intensive solar radiation (sunshine) onthe vehicle can raise the interior temper-ature by 20°C (69°F) To 25°C (77°F)above the outside temperature, particu-larly in the head area where the heat isperceived as most unpleasant.• The body temperature rises and theheart rate increases. This situation is alsocharacterized by increase perspiration.• The brain receives too little oxygen. ZoneBis characterized by moderate climaticstrain.• ZoneCposes an overload situation forthe body, often referred to as "climaticstress".Index12345A,B,CExplanationStressClimatic StressPerspirationHeart rateBody temperatureComfort zoneNote: Research shows that sensory perception and powers of deductiondecrease by 20% at a temperature increase from 25 to 35°C (77 to 95°F)5Principles of Heating and Refrigeration [ Pobierz całość w formacie PDF ]

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