Frost Damage in Heat Pipes

German manufactured products are famous for being rigorously tested. One of the leading test institutes is TUV Rheinland which has a special expertise in testing thermal solar evacuated tubes. Evacuated tube solar collectors were originally designed by Dornier in Germany. There are various kinds of evacuated tubes but one popular and expensive kind is the tube which contains a heat pipe – a sealed pipe which usually contains a fluid which expands and contracts according to the heat and delivers heat through a manifold through which a freeze resistant glycol is passed as a heat exchange medium.

These are not the kind of solar collectors that my company manufacture. I have written extensively about the advantages and disadvantages of evacuated tubes and concluded that apart from in specialist situations where there is a lack of roof space you will get better performance, fewer maintenance issues and better value with flat plate solar collectors. After all, an evacuated tube is a bit like a light bulb – when the vacuum is lost the performance is reduced and the tube that has lost its vacuum must be replaced, which is usually expensive especially of the tube is mounted on a roof.

TUV Rheinland has now warned of another issue affected evacuated tubes, which came to light after the recent very cold winter. Like Britain, the last winter in Germany was exceptionally cold. At the end of the very cold winter many larger evacuated tube thermal solar installations reported than a large number of heat pipes had burst due to frost damage. Burst heat pipes in evacuated tubes render the tubes useless. While they were thought to be frost proof (previously most evacuated tube problems arose with overheating issues) it is now clear, TUV Rheinland report, notwithstanding what was believed previously, heat pipes are not frost proof.

One Response

  1. Thanks for the news.

    Here some more detailed informations:

    http://www.boards.ie/vbulletin/showthread.php?t=2056381258

    It wasn’t the vacuum which failed. The evacuation was still there with the failed HPs.
    The copper pipe bursted, the pipe within the vacuum tube holding the thermal carrier fluid.
    The old test program tested the collectors, not the individual tubes/heat pipes. For half an hour they were exposed to frost.
    The new test program lasts for 10 hours.

    HB

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