Heat-Transfer Fluid Maintenance for Liquid-Phase Systems | AIChE

Heat-Transfer Fluid Maintenance for Liquid-Phase Systems

This article introduces the basic characteristics of heat transfer fluids and describes the methods by which a heat transfer fluid may degrade. It also gives readers information on the numerous factors that must be considered before choosing a heat transfer fluid.

Heat transfer fluids are employed to carry thermal energy away from a heat source to a different location in the system. There are two categories of systems in which heat transfer fluids are used — open and closed systems. In an open system, the heat transfer fluid comes in direct contact with the atmosphere. In a closed system, the heated oil does not come in direct contact with the atmosphere. When heat transfer fluid is circulated via piping, the tubeskin temperature is the temperature of the fluid molecules that are in contact with the pipe wall. It is imperative to carefully monitor the tubeskin temperature, as sudden temperature spikes may result in thermal cracking or auto-ignition of the heat transfer fluid.

Degradation of heat transfer fluids is typically due to one (or more) of three primary causes: thermal degradation, oxidative degradation, and contamination. Thermal degradation occurs when the fluid is exposed to more heat than it can absorb, which results in thermal cracking. Oxidation occurs when the fluid is exposed to oxygen, which causes degradation, varnishing, and formation of heavy insoluble compounds. Contamination can cause severe system damage, and may be the result of process leaks, previous pressure-testing fluid in the system, or improper oil storage.

When selecting a heat transfer fluid, you must consider several factors, which include: purchase price, disposal methods, safety, fluid change-out cycles, fluid analysis, and seal replacement time, among others.

Tags 

Heat-transfer fluids
Heaters
Reboilers
Coolers
Heat Exchangers
Jacketed reactors
Jacketed blenders
Distillation units

Date 

January, 2015