In the past, ice was been used to achieve refrigeration. This involves natural refrigeration.
The principle behind this is known as evaporative cooling. In the past ice was either:
1. Transported from colder regions,
2. Harvested in winter and stored in ice houses for summer use or,
3. By cooling of water by radiation to stratosphere (During Night).
In Europe, America and Iran a number of ice houses were built to store ice. Ice houses were made with sawdust or wood shavings as insulating materials. Later on, cork was used as insulating material. Literature states that ice has been available to aristocracy who could afford it. In India, the Mogul emperors were interested of ice during the violent summer in Delhi and Agra, and it seems that the ice was used to be made by nocturnal cooling.
In 1806, Frederic Tudor, (who was known as the “ice king”) introduced the trade of ice by cutting it from the Hudson River and ponds of Massachusetts and exporting it to various countries such as India. In India Tudor’s ice was cheaper than the locally manufactured ice by nocturnal cooling. In North America, ice business emerged as a flourishing business. Ice was insulated by 0.3m of cork in order to transport it to southern states of America in train.Trading in ice was also popular in several other countries such as Great Britain, Russia, Canada, Norway and France. In these countries ice was either transported from colder regions or was harvested in winter and stored in ice houses for use in summer.
The ice trade reached its peak in 1872 when America alone exported 225000 tons of ice to various countries as far as China and Australia. However, with the invention of modern refrigerator the ice trade gradually declined.
Art of Ice making by Nocturnal Cooling:
The art of making ice by nocturnal cooling was perfected in India. In this method ice was made by keeping a thin layer of water in a shallow earthen tray, and then exposing the tray to the night sky. Compacted hay of about 0.3 m thickness was used as insulation. The water loses heat by radiation to the stratosphere, which is at around -55 ̊C and by early morning hours the water in the trays freezes to ice. This method of ice production was very popular in India.
As the name indicates, evaporative cooling is the process of reducing the temperature of a system by evaporation of water. Human beings perspire and dissipate their metabolic heat by evaporative cooling if the ambient temperature is more than skin temperature. Animals such as the hippopotamus and buffalo coat themselves with mud for evaporative cooling.Evaporative cooling has been used in India for centuries to obtain cold water in summer by storing the water in earthen pots. The water permeates through the pores of earthen vessel to its outer surface where it evaporates to the surrounding, absorbing its latent heat in part from the vessel, which cools the water. It is said that Patliputra University situated on the
bank of river Ganges used to induce the evaporative-cooled air from the river.Suitably located chimneys in the rooms augmented the upward flow of warm air, which was replaced by cool air. Evaporative cooling by placing wet straw mats on the windows is also very common in India. The straw mat made from “khus” adds its inherent perfume also to the air. Nowadays desert coolers are being used in hot and dry areas to provide cooling in summer.