CASES & ENCLOSURES FEATURE
Passive cooling of instrumentation shelters is often used in desert climates, however
hybridised versions of the technology are now making their way into different locations and applications, as Martin Hess and Keith Wood, Intertec Instrumentation, explain
PASSIVE COOLING: A mainstream solution?
Using forced circulation extends the
location potential of passive cooling because such cooling relies on a reasonable temperature differential to power the natural convection cycle that moves the water around the system. Micro pumps reduce the dependence on a wide day/night temperature difference - opening up applications in areas beyond traditional arid climates. Such systems are used often on SCADA
shelters along pipelines – see Figure 1, which shows an example on a drinking water pipeline in the UAE. Control and instrumentation at remote wellheads is another major application, as in Figure 2.
P
assive cooling is widely used in desert and semi-desert climates, often for
control and instrumentation shelters on pipelines, or at remote sites that are off-grid or located where the power supply is unreliable. In fact the technique is ideal for climates where there is a large temperature swing over the daily cycle – this can be exploited by using water as a medium to store the coolness of the night and use it to moderate temperatures throughout the day. In recent years, however, hybridised
forms of passive cooling have been developed which significantly extend the location and application possibilities of this technology. These can extend the capability of the cooling technology to applications in Europe, in equatorial regions and offshore. Intertec employs two main techniques to extend the scope of passive cooling. One is the use of micro pumps – which can be powered by small solar panels – to improve the circulation of the cooling media. The second is the augmentation of the performance of the cooling media – which is typically water – by
using cooler or chilled water. At the heart of these solutions is the use of highly insulated enclosures, which utilise composite constructions of GRP inner and outer walls, plus a thick core of embedded insulation.
FORCED CIRCULATION Small 12VDC-powered pumps are available to improve the circulation of the cooling media. As a rule of thumb, these can
A COOLER SOLUTION A second technique to improve the performance of water-based passive cooling is to exploit the availability of any nearby cooler water – which might come from a river, underground source or the sea. The water only needs to be cooler than the required interior temperature by 2-3˚K to provide a good solution. This type of design can significantly reduce the size of the cabinet or shelter – or even eliminate the need for a water storage tank – and extend the geographical areas in which this type of cooling is applicable. A high profile example of this
technology is on the Prelude floating liquefied natural gas vessel, which will
“Intertec employs two main techniques to extend the scope of passive cooling. One is the use of micro pumps to improve the circulation of the cooling media. The second is the augmentation of the performance of the cooling media by using cooler of chilled water. At the heart of these solutions is the use of highly insulated enclosures”
double the performance of a passive cooler. The electrical energy consumption of these pumps is typically only around 10W; so while the required electrical energy might be available on site, it could be provided by a small solar panel.
be sited in an equatorial region near Timor. Intertec has supplied some 120 instrumentation and analyser cabinets for the vessel, which will be cooled using ‘cold’ water from a 150m long pipe into the ocean.
INSTRUMENTATION | NOVEMBER 2016
Figure 1. A remote SCADA shelter cooled by a passive water-based system with forced circulation of media - powered by solar panels
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