What does space is cold mean

cold

Lexicon> letter K> cold

Definition: a lack or withdrawal of heat

More specific terms: district cooling

English: cold, cooling

Categories: Basic Terms, Physical Basics, Heat and Cold

Author: Dr. Rüdiger Paschotta

How to quote; suggest additional literature

Original creation: May 27, 2010; last change: 15.05.2021

URL: https://www.energie-lexikon.info/kaelte.html

The extraction of thermal energy, i.e. the supply of cold, can also be worth money!

The term cold is used with slightly different meanings:

  • Sometimes a perceived lack of warmth is meant. For example, one suffers from cold when a room is insufficiently heated.
  • In other cases it becomes cold generated or delivered (see below). This is mostly about cooling down to a temperature below the ambient temperature. For this it is not enough, e.g. B. to bring the object to be cooled into thermal contact with the surrounding air so that it gives off heat to this. Rather, becomes a Chiller needed, which can extract heat from the object, even if it is already relatively cold, and gives off this heat to a warmer environment.

Laypeople often understand cold as a kind of antagonist to warmth. One speaks z. B. from the fact that in winter cold penetrates the house through the walls. In physics, however, this is usually described in reverse so that heat flows out of the warm house. Accordingly, one speaks z. B. from Thermal bridges and not from Cold bridges.

Generation of cold; Cold and exergy

The generation of cold in the sense of extracting heat from objects that are already colder than the environment usually requires exergy (drive energy) to operate a Chiller. This contains a heat pump that can “pump” heat from a colder to a warmer reservoir, but requires drive energy to do so. (“Voluntarily” heat would only flow in the other direction: from the warmer to the colder body.) The relative expenditure of drive energy is higher, the further the required temperature is below the ambient temperature at which the cooling machine can emit the heat. This means that there are e.g. B. costs much more energy with an air conditioner 1 m3 Cooling air by 10 degrees than 10 m3 by 1 degree. Likewise, z. B. the electricity demand of a refrigerator if the condenser on the back, through which the waste heat has to be dissipated, is dusty and is therefore particularly warm.

Conversely, a cold reservoir could be used to generate mechanical and electrical energy by operating a heat engine between the warmer environment and the cold reservoir. In this case, part of the ambient heat is converted into electrical energy, and the rest has to be absorbed by the cold reservoir.

Cold can also be generated with little exergy, e.g. B. water is evaporated and absorbs the heat of evaporation. The water vapor can then be released into the environment. This of course requires a replenishment of water; it is not a closed system like a refrigeration machine.

Methods of "free cooling”Make use of the cold from the environment in order to greatly reduce energy consumption.

Transportation of cold

Cold can be transported by transporting a cold medium - often water. For example, district cooling is transported in pipeline networks in which cold water is sent to the cooling consumers and then flows back heated.

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See also: heat, refrigerator, air conditioning, chiller, split air conditioner, district cooling, heat pump, combined heat and power, free cooling, exergy, temperature
as well as other articles in the categories basic concepts, physical principles, heat and cold