【正文】 infiltration, insulation, solar effect, and noise. Ambient and Vehicle Criteria Ambient Temperature. Heaters are evaluated for performance at temperatures from ?40 to 21176。 (3) it generally reduces the number and plexity of driver controls。山東建筑大學(xué)畢業(yè)設(shè)計(jì)外文文獻(xiàn)及譯文 1AUTOMOBILE AIR CONDITIONING ENVIRONMENTAL control in modern automobiles consists E of one or more of the following systems: (1) heaterdefroster,(2) ventilation, and (3) cooling and dehumidifying (airconditioning). All passenger cars sold in the United States must meet federal defroster requirements, so ventilation systems and heaters are included in the basic vehicle design. The integration of the heater defroster and ventilation systems is mon. Air conditioning remains an extracost option on many vehicles. Heating Outdoor air passes through a heater core, using engine coolant as a heat source. To avoid visibilityreducing condensation on the glass due to raised air dew point from occupant respiration and interior moisture gains, interior air should not recirculate through the heater. Temperature control is achieved by either water flow regulation or heater air bypass and subsequent mixing. A bination of ram effect from forward movement of the car and the electrically driven blower provides the airflow. Heater air is generally distributed into the lower forward partment, under the front seat, and up into the rear partment. Heater air exhausts through body leakage points. At higher vehicle speeds, the increased heater air quantity (ram assist through the ventilation system) partly pensates for the infiltration increase. Air exhausters are sometimes installed to increase airflow and reduce the noise of air escaping from the car. The heater air distribution system is usually adjustable between the diffusers along the floor and on the dashboard. Supplementary ducts are sometimes required when consoles, panelmounted air conditioners, or rear seat heaters are installed. Supplementary heaters are frequently available for thirdseat passengers in station wagons and for the rear seats in limousines and luxury sedans. Defrosting Some heated outdoor air is ducted from the heater core to defroster outlets at the base of the windshield. This air absorbs moisture from the interior surface of the windshield and raises the glass temperature above the interior dew point. Induced outdoor air has a lower dew point than the air inside the vehicle, which absorbs moisture from the occupants and car interior. Heated air provides the energy necessary to melt or sublime ice and snow from the glass exterior. The defroster air distribution pattern on the windshield is developed by test for conformity with federal standards, satisfactory distribution, and rapid defrost. Most automobiles operate the airconditioning pressor to dry the induced outdoor air and/or to prevent a wet evaporator from increasing the dew point when the pressor is disengaged. Some vehicles are equipped with side window demisters that direct a small amount of heated air and/or air with lowered dew point to the front side windows. Rear windows are defrosted primarily by heating wires embedded in the glass. Ventilation Fresh air is introduced either by (1) ram air or (2) forced air. In both systems, air enters the 山東建筑大學(xué)畢業(yè)設(shè)計(jì)外文文獻(xiàn)及譯文 2 vehicle through a screened opening in the cowl just forward of the base of the windshield. The cowl plenum is usually an integral part of the vehicle structure. Air entering this plenum can also supply the heater and evaporator cores. In the ram air system, ventilation air flows back and up toward the front seat occupants’ laps and then over the remainder of their bodies. Additional ventilation occurs by turbulence and air exchange through open windows. Directional control of ventilation air is frequently unavailable. Airflow rate varies with relative windvehicle velocity but may be adjusted with windows or vents. Forced air ventilation is available in many automobiles. The cowl inlet plenum and heater/airconditioning blower are used together with instrument panel outlets for directional control. Po