【正文】 sitive air pressure from the ventilation fan or blower helps reduce the amount of exterior pollutants entering the passenger partment. In airconditioned vehicles, the forced air ventilation system uses the airconditioning outlets. Body air exhausts and vent windows exhaust air from the vehicle. With the increased popularity of air conditioning and forced ventilation, most late model vehicles are not equipped with vent windows. Air Conditioning Air conditioners are installed either with a bination evaporatorheater or as an addon system. The bination evaporatorheater in conjunction with the ventilation system is the prevalent type of factoryinstalled air conditioning. This system is popular because (1) it permits dual use of ponents such as blower motors, outdoor air ducts, and structure。 (2) it permits promise standards where space considerations dictate (ventilation reduction on airconditioned cars)。 and (4) it typically features capacity control innovations such as automatic reheat. Outlets in the instrument panel distribute air to the car interior. These are individually adjustable, and some have individual shutoffs. The dashboard end outlets are for the driver and front seat passenger。C. Airconditioning systems with reheat are evaluated from 4 to 43176。 addon units are evaluated from 10 to 38176。C are occasionally encountered. Because the system is an integral part of the vehicle detail, the effects of vehicle heat and local heating must be considered. Ambient Contaminants. Airborne bacteria, pollutants, and corrosion agents must also be considered when selecting materials for seals and heat exchangers. Electronic air cleaners and filters have been installed in premium automobiles. Vehicle Performance . Proper engine coolant temperature, freedom from gasoline vapor lock, adequate electrical charging system, acceptable vehicle ride, minimum surge due to pressor clutch cycling, and good handling must be maintained. Flexibility . Engine coolant pressure at the heater core inlet ranges up to 280 kPa (gage) in cars and 380 kPa on trucks. The engine coolant thermostat remains closed until coolant temperature reaches 71 to 96176。K) and boiling points from 121 to 133176。 (2) drive ratio, from :1 to :1。C and from 150 to 1400 L/s (corrected for restriction and distribution factors)。C. Physical Parameters Parameters include engine rock, proximity to adverse environments, and Rock. Relative to the rest of the car, the engine moves both fore and aft because of inertia and in rotation because of torque. Fore and aft movement may be as much as 6 mm。 65 km/h = 4000 h), but the shock and vibration the vehicle receives or produces must not cause a malfunction or failure. Equipment is designed to meet the remendations of SAE Remended Practice J 639, which states that the burst strength of those ponents subjected to highside refrigerant pressure must be at least times the venting pressure (or pressure equivalent to venting temperature) of the relief device. SAE J 639 also requires electrical cutout of the clutch coil prior to pressure relief to prevent unnecessary refrigerant discharge. Components for the lowpressure side frequently have burst strengths in excess of 2 MPa. The relief device should be located as close as possible to the discharge gas side of the pressor, preferably in the pressor itself. Power and Capacity Fan size is kept to a minimum not only to save space and reduce weight, but also to reduce energy consumption. If a standard vehicle has a heater that draws 10 A, and the air conditioner requires 20 A, the alternator and wiring must be redesigned to supply this additional 10 A, with obvious cost and weight refrigeration capacity must be adequate to reduce the vehicle interior to a fortable temperature quickly and then to maintain the selected temperature at reasonable humidity during all operating conditions and environments. A design may be established by mathematical modeling or empirical evaluation of all the known and predicted factors. A design tradeoff in capacity is sought relative to the vehicle’s weight, ponent si