Clean Air and Containment Review
The journal to enhance your knowledge of cleanroom, clean air and containment technology

Issue 14: April 2013
Main features
Removal efficiency of high efficiency air filters against microbe-carrying particles
(MCPs) in cleanrooms
W Whyte, G Green and WM Whyte
School of Engineering, University of Glasgow, G12 8QQ
The removal efficiency of high efficiency air filters was determined against microbe carrying particles (MCPs) in the air supply to cleanrooms. Knowing the size distribution of MCPs in the air to be filtered, and the filter's removal efficiency against individual particle diameters, the overall removal efficiency was ascertained. The removal efficiency of individual species of microbes with a known size was also obtained. A variety of filters were investigated, and it was found that a filter 90% efficient against the most penetrating particle size (as classified by EN 1822) was greater than 99.99% efficient in removing a MCPs. The effect of filter efficiency on the microbial concentration in both the air supply and the cleanroom air was studied, and no practical improvement in the air quality was obtained by filters that had a removal efficiency greater than 99.99% against MCPs. Use of a filter suitable for removing MCPs, rather than sub-micrometre particles, would give a reduction of about 6 to 8-fold in the pressure differential across the filter, and a substantial reduction in the energy costs of running a cleanroom.

Key words: removal efficiency, microbes, micro-organisms, high efficiency air filters, HEPA, cleanrooms, energy efficiency, fan power.
Energy saving opportunities in cooling systems for cleanrooms
Gordon Farquharson
This article describes a number of energy saving measures that can be implemented in cooling systems for cleanrooms. Some of these arise from a better understanding of the physics of refrigeration and others from advances in the design of systems and components. Amongst the ideas discussed are the separation of chilled water cooling systems into those for latent heat and those for sensible heat, the application of refrigerant liquid pressure amplification (LPA) to allow operation of refrigerant circuits at lower discharge pressures, the use of electronic expansion valves to achieve closer control and energy savings in refrigerant circuits, electronically commutated (EC) condenser fan motors, improvements in refrigerant compressor technology and in heat transfer coil technology, enhanced free cooling and, finally, advances in desiccant dehumidification. All of these developments can provide worthwhile energy reductions when incorporated into designs for new cleanroom air conditioning plants and many of them can be retrofitted to existing plants.
Fans with EC (Electronically commutated) motors
Gunter Streng

The much-used term "efficiency" describes the ratio of output to the input needed to generate it. This is by no means restricted to energy efficiency. In fan technology, the focus is certainly on energy efficiency, not least in order to satisfy the ever stricter future directives. Energy-efficient EC technology is increasingly the technology of choice. However, just as important are production efficiency (minimising production down-time), by the use of reliable easy-to-install 'plug-and-play' solutions, and manufacturing efficiency resulting from designs with fewer individual parts. EC fan motor technology has now developed to the point where all these benefits are available for the user.
New Cleanroom Energy Management Standard:
BS 8568:2013 - Cleanroom energy - Code of practice for improving energy efficiency in cleanrooms and clean air devices
Dick Gibbons
Revision of ISO 14698 - Biocontamination control:
Personal reflections of what might be desirable
Tim Sandle

Vital vocabulary
V is for...

Contec, Cavendish, Pharminox, Esco, Energy & Carbon, CRC, Validair

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