Object StatementCold air machine, steam powered, for refrigerating ships' cargoes, cast iron / steel / wood, made by Haslam Foundry & Engineering Co Ltd, Derby, England, 1882-1895
Physical DescriptionThis Haslam cold air machine was designed to produce 2000 cubic feet (57,000 litres) of cold air per hour. It consists of a vertical single-cylinder double-acting steam engine, cold-air compressor, heat exchanger, expander and water pump. The steam engine drives a crankshaft, which drives the tandem arrangement for compression and expansion of air, which acts as the refrigerant. The compression cylinder is mounted above the expansion cylinder, and their pistons are attached to a common rod. An eccentric on the crankshaft actuates the steam slide valve, which controls the admission of steam to the engine's cylinder.
Air at atmospheric pressure is drawn into the compression cylinder through an intake valve. As it is compressed, its temperature rises. The hot compressed air then passes to the water-cooled heat exchanger. The cooled air is admitted to the expansion cylinder through expansion and cut-off valves. As the piston rises, the cut-off valve stops the admission of compressed air to the cylinder, which reduces the pressure, and thus the temperature, of the air. Subsequently, near top dead centre, the expansion valve opens and, on the downward stroke of the piston, the cold air is expelled.
The temperature of the delivered air is controlled by the timing of the opening of the cut-off valve. The cycle theoretically follows the reversed Brayton cycle, comprising isentropic compression, constant pressure cooling, isentropic expansion and, finally, constant pressure discharge to either refrigerant coils or discharge into a cold room. An isentropic process is a reversible adiabatic process, or a reversible process having no heat exchange with the working fluid.
All cylinders have 250 mm stroke. Cylinder bores are: steam 120 mm, compression 235 mm, expansion 155 mm. The expansion cylinder has wood lagging over a straw-like insulating material. There are two flywheels.