Lightweight Cooling Unit
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for Coaches and Vans
How the Problem of Heating and Air-conditioning of Passenger Vehicles is Tackled in the United States
THE self-contained refrigerating unit shown in the accompanying illustrations represents the main component of an air-conditioning system, for motor coaches, that has been developed in the United States, through the c4-operation of engineers of the Waukesha Motor Co., Tropic Aire., Inc., and the Greyhound Lines. Claimed to be the lightest, most compact and efficient cooling unit yet devised for road-transport work, it is being offered to coachbuilders and operators for general installation and use,
In evolving the system, the experience of the Waukesha concern, in building and perfecting plant for the railways, and of Tropic Aire, Inc., in designing heating systems for motor vehicles, was combined to produce an all-the-yearround system for cooling, heating, filtering, dehumidifying and circulating the air in buses and coaches.
The result is a power cooling unit weighing less than 400 lb., with the moderate overall dimensions of 17 ins. by 24 ins. by 44-1 ins. It can easily be rolled out, for inspecting and servicing, from a compartment under the floor of the vehicle, and it is interchangeable, readily and quickly, from one machine to another. Refrigeration is at a rate equivalent to the melting of three to four tons of ice in 24 hours, with air admitted to the refrigerant condenser at 90 degrees F.
The principal elements of the unit are a specially designed lightweight, four-cylindered petrol engine, developing 14 h.p. at 1,800 r.p.m. and 18.2 h.p. at 2,400 r.p.m.; a directdriven, rotary, refrigerant compressor; an evaporative-type condenser for liquefying the, refrigerant; a positive-drive, water-circulating pump and spray nozzles for the condenser; a permanent-type air filter; a blower-type direct-drit en air fan, having a capacity of 900 cubic ft. per minute, for supplying cooling air to the condenser, engine radiator and interior of the cabinet ; a steel cabinet, built up on a welded steel frame, mounted on six ball-bearing wheels; steel tracks, supported on rubber, for withdrawing the unit from its compartment in the vehicle; flexible connections for the refrigerant, water supply and electrical lines; cut-outs for high and low-refrigerant pressure, and engine overheating; and provision for thermostatic control from inside the coach.
No attention is required from the driver, as a thermostat automatically controls starting and stopping of the engine, and its speed. As the demand for cooling decreases, a control comes into action to reduce the speed of the unit, so that the cooling coils are maintained at a temperature low enough to keep down humidity, without further reduction of temperature.
Passenger comfort is assured, even under -extreme conditions of heat, as the capacity is claimed to be sufficient to maintain a temperature differential, as between inside and outside conditions, of from 15 degrees F. to 40 degrees F.
This self-contained unit is intended for housing within a dust-tight compartment in the vehicle, so arranged that all air entering the compartment, for cooling the engine and condenser and for ventilating the cabinet, will be filtered and, subsequently, discharged from the bottom of the unit.
Expansion of the refrigerant, for absorbing heat from the air within the coach, takes place in an evaporating unit installed under the cab roof. Tropic Aire, Inc., makes these units, in various types and capacities, to meet specific service requirements. The heating system is a separate installation, its capacity being in accordance with the size of the vehicle and the extent of the heating required.
The auxiliary water supply, which ha,s to be arranged for by the vehicle builder or operator. must have a capacity sufficient to provide for a consumption of from four gallons to seven gallons per hour, a feature governed by service conditions.