How did the ancients refrigerate? This type of air conditioning is more energy-efficient!

Summer has come, and it is the season to eat barbecue and drink beer. We often see diners blowing air conditioners, drinking beer and feasting on Market stall

Summer has come, and it is the season to eat barbecue and drink beer. We often see diners blowing air conditioners, drinking beer and feasting on Market stall.

I don't know if you have ever observed that this kind of air conditioning fan is not the type of air conditioner installed in our office or home. This kind of air conditioning fan and outdoor spray cooling even have the same principle as the ancient "Self Rain Pavilion" and "Hanliang Hall". They actually use evaporative cooling.

Air conditioning fan, outdoor spray system and self rain pavilion

Evaporative cooling is a process of cooling air through the evaporation of water, where water absorbs heat from the air and evaporates to cool it.

The drier the air, the stronger its ability to hold water. When using water to spray the air, the greater the decrease in air temperature. If using lower temperature tap water or well water, the cooling effect of the air is better.

Therefore, in high-temperature and dry environments, using evaporative cooling air conditioning fans to cool the air consumes much less electricity than using air conditioners, thus having good energy-saving effects.

However, the moisture content that can be accommodated in the air is limited (increasing the water content after reaching the limit will flow out of the air in the form of liquid water). Therefore, the temperature of low-temperature air that can be produced by evaporative cooling is limited by this characteristic, making it impossible to produce very low temperature air.

Thousands of years ago, Ancient Egypt and Persia used evaporative cooling air conditioners in the form of roof air shaft "air traps". The "wind catcher" is set up against the wind, and air flows down the air shaft into the fountain inside the building, then sends the cooled air into the room.

Wind catchers with windshields and indoor fountains in the Middle East (murals from the 2nd century BC)

In ancient China, there were also records of evaporative cooling air conditioning. During the Han Dynasty, inventor Ding Xun invented the seven wheeled fan, which was connected to seven wheels and had a diameter of ten meters (Volume 1 of "Miscellaneous Records of Xijing"). Later generations used hydraulic power to drive it and introduce water flow to the location of air flow, not only providing power but also using evaporative cooling to reduce air temperature, It makes people feel that "it is cold and rustling, it is not silk or bamboo, and the sounds of nature are heard from afar" (Qianlong's "Ode to Forty Scenes of the Old Summer Palace").

Similar to the Ziyu Pavilion and Hanliang Hall, there is a poem saying that "amber lamps are red, and the crystal curtain is more ventilated (Liu Yuxi's" Liu Fuma's Water Pavilion for Summer Vacation ")", which conveys cold water to the top, and then flows down from the eaves to form a water curtain, playing the role of summer cooling.

The estimate includes the principle of cool hall, 40 scenes of water and wood in Old Summer Palace

In ancient times, using the principle of evaporative cooling to escape the heat and enjoy a cool summer was often a service that only high-ranking officials and nobles could enjoy. Nowadays, with the development of society, air conditioners and multi line machines that use electricity to drive refrigeration have already flown into ordinary households. However, evaporative cooling still plays an irreplaceable role.

Evaporative cooling has transformed from a simple ventilation and cooling method to an energy-saving and green technology that utilizes renewable energy sources such as dry air, effectively promoting the achievement of "carbon peaking and carbon neutrality".

In arid or semi-arid areas of the western region, many industrial buildings can completely replace mechanical refrigeration air conditioning systems with evaporative cooling air systems. In humid and semi humid areas, dew point evaporative cooling can also be used to achieve refrigeration, thereby improving the working environment of workshops.

In the era of Big data, the communication machine room and data center operate continuously throughout the year, and the energy consumption continues to increase. In winter or transitional seasons, the use of evaporative cooling technology, combined with indirect evaporative cooling and precooling in summer, can significantly reduce the annual energy consumption.

Evaporative cooling also plays an irreplaceable role in household air conditioning. In addition to the air conditioning fans mentioned earlier, evaporative cooling can also be combined with new household air conditioning technologies.

In the Global Refrigeration Technology Innovation Grand Prix held in 2021, the Chinese team proposed the air conditioner scheme of "advanced Vapor-compression refrigeration technology integrating evaporative cooling and solar photovoltaic", which organically combines evaporative cooling, solar photovoltaic and efficient refrigeration systems, realizes the efficient energy saving of air conditioners and the accurate control of indoor temperature and humidity, and stands out from more than 2100 teams to win the championship.

The technology uses evaporative cooling to regulate the indoor environment by taking dry air as a means, combined with climate adaptive ventilation control technology, to realize the functions of ventilation, cooling and dehumidification, opening up a new direction for the development of air conditioning technology.

By combining evaporative cooling, a technology with thousands of years of application history, with new technologies, we can explore the application value and energy-saving potential of evaporative cooling, thereby contributing more wisdom, solutions, and strength to global energy conservation, emission reduction, and low-carbon transformation, and injecting strong momentum into green development.

Award Ceremony of the Global Refrigeration Technology Innovation Awards

Reference:

[1] Kheirabadi, Masoud (1991). Iranian cities: formation and development. Austin, TX: University of Texas Press

[2] Xu Aiqing. What are the tips for ancient people to avoid summer heat [J]. Science Grand View Park, 2022, No.645 (13): 72-75

END

Author: Yang Zixu, postdoctoral fellow, Department of Architectural Technology and Science, Tsinghua University

Contributed by: Beijing Refrigeration Society

(Some illustrations are sourced from the internet)

Editor in Chief: Gulu

Source: Tadpole Staff

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