MARLOTHERM® LH is a high-performance synthetic, organic heat-transfer medium for use in the liquid phase and in the vapour-liquid phase in closed, forced circulation heat transfer systems. The upper use limit lies at a heater outlet temperature of 360°C (680°F). The film temperature should not exceed the limit of 380°C (716°F) significantly or for a prolonged period.
MARLOTHERM® LH in the liquid phase is preferably used in unpressurized systems at working temperatures from 0° to 280°C (32°F to 536°F). Due to its favourable viscosity behaviour, MARLOTHERM® LH is an ideal heat-transfer medium for heating and cooling processes.
- In customary heat exchangers, it provides good heat transfer down to temperatures around 0°C. At working temperatures below 0°C, the heat-exchange surface is to be matched to the technical characteristics of MARLOTHERM® LH and the flow conditions.
- best suited to the temperature control of vessels, reactors and processing machines which are both heated and cooled by means of a central heat-transfer system, and in systems in which several consumers have to be supplied at very different temperature levels.
- can be used at working temperatures above 280°C in pressurized systems. The advantage offered by the use of MARLOTHERM® LH in this temperature range compared with ”pressureless“ use of MARLOTHERM® SH has to be assessed in each individual case. Owing to its narrow boiling range of about 4°C, MARLOTHERM® LH can also be used in the vapour-liquid phase, e.g. for reactor cooling in exothermic processes.
Heat transfer plants containing MARLOTHERM® LH can be started up without difficulty at temperatures down to about -30°C (-22°F) using centrifugal pumps with a rotating mechanical seal or permanent magnet drive, or using canned motor pumps. At operating temperatures below the boiling point of the heat-transfer medium, MARLOTHERM® LH circuits are most efficiently operated using an inert gas back pressure of less than 100 mbar at the expansion vessel. Nitrogen is suitable as an inert gas. Inert gas blanketing is the best protection against changes in the heat-transfer charge caused by oxidation. Antioxidants are unstable at operating temperatures above 200°C and are ineffective even after short operating times. At operating temperatures above the boiling point of MARLOTHERM® LH, it is necessary to apply an inert gas back pressure which is sufficient to keep the heat-transfer medium in the liquid state and prevent vaporization via the expansion vessel.