A method and apparatus for separately supporting and sealing a heat pipe within a heat exchanger. For support, the heat pipe with fins thereon passes through a support grid which consists of a series of rings secured or interconnected together. The fins of the heat pipe rest upon these rings of the support grid thereby supporting this region of the heat pipe. To seal these heat pipes in order to prevent any gas escape from the heat exchanger, a tubesheet with openings therein is placed over the ends of the heat pipe. These openings are oversized thus a considerable gap exists between the tubesheet and the heat pipe. This gap is covered or sealed by use of a cover disk which tightly fits around the heat pipe and spans across this gap before it is removably secured to the tubesheet. By this fashion, once the cover disk is removed from the tubesheet, it is a relatively easy task to then remove the tubesheet and the heat pipe from the heat exchanger for maintenance or repair purposes.

Disclosed is a refrigerator comprising an outer casing defining an outer appearance thereof, and an inner casing accommodated in the outer casing, forming a storage chamber, further comprising a heat pipe unit having an evaporator pipe disposed to surround at least one portion of the inner casing, forming a refrigerant path, a heater pipe disposed in parallel with the evaporator pipe, and a connection part connecting the evaporator pipe and the heater pipe, enabling a heat transfer therebetween. With this configuration, there is provided a refrigerator enhancing cooling, ripeness and defrost performances and the productivity.

An apparatus for the controlled heating of a process fluid has a heater, a process fluid vessel containing the process fluid, and a bundle of thermosyphons extending between a burner chamber of the heater and the process fluid inside the vessel for transferring heat from the heater to the process fluid. Burners in the burner chamber are controlled to maintain the bulk temperature of the process fluid T.sub.BULK substantially within an operating range defined by preset upper T.sub.HIGH and lower T.sub.LOW temperature setpoints. The burners can be turned on to maintain an outside metal temperature T.sub.EVAP of the evaporator ends of the thermosyphons above a preset dew point temperature T.sub.DEW to prevent corrosion. The burners can also be shut down if an outside surface temperature T.sub.OD of at least one of the condenser ends of the thermosyphons extending into the vessel exceeds a predetermined setpoint temperature T.sub.ALARM. Different configurations of condenser ends of the thermosyphons in the vessel may be utilized to enhance heating the process fluid. The vessel and heater are separated and sealed from each other by a sealed chamber encasing the thermosyphons, which may also be used to preheat incoming combustion air for the burners.