tCold

Tcold is a term used in thermodynamics and cooling technology to designate the temperature at the cold side of a thermal system. It is most commonly encountered in analyses of refrigeration cycles, cryogenic cooling, and liquid-plant operations. Tcold is usually defined as the lowest temperature that the system can maintain at its cold reservoir or cold stage, and it is often contrasted with Thot, the corresponding hot-side temperature. The difference ΔT = Thot − Tcold is a key parameter in assessing performance, along with the coefficient of performance (COP), efficiency, and refrigerant properties.

Measurement and control: Tcold is measured with sensors such as thermocouples or resistance temperature detectors placed at the cold surface or in the cold transfer fluid. Control systems adjust compressors, valves, and heat exchangers to keep Tcold within target limits, balancing load, energy use, and stability.

Technologies: The Tcold value can be achieved by several cooling cycles. In domestic and industrial refrigeration, vapor-compression cycles produce moderate Tcold. In cryogenics, specialized coolers such as Stirling, pulse-tube, and dilution refrigerators push Tcold toward cryogenic temperatures. The specific Tcold target depends on application, from sub-zero to near 4 K.

Notes: Tcold is a variable name common in system diagrams and thermal models; it is sometimes written as Tc or Tcold. In literature, more descriptive terms like cold-side temperature or evaporator temperature are used when context favors readability.

See also: Thot, COP, cryogenics, heat exchanger.