Keeping Cold Rooms Cold

During normal operation of a Climate Controlled Room or Cabinet the cooler's heat exchanger coils (the cold source) are slowly encased in a film of ice.  This is caused by the air borne moisture in the ambient air sublimating on contact with the cold heat exchanger coils of the cooler and forming ice. This ice build-up is slow, progressive and inexorable.  It can; if left unchecked, transform the heat exchanger coils into a useless block of solid ice.

The ice build-up is heavily dependent on ambient conditions.  If the heat exchanger was positioned or used air drawn from a climatically controlled area (low humidity), this ice build-up would be totally different from an installation that was expose to near saturated air conditions.  To allow for these ambient atmospheric variations, the defrost cycle is usually controlled by time.  So during the commissioning study stages, the requisite time interval between defrost cycles must be established.

The most common design methodology for defrosting the heat exchanger coils is simply to incorporate in the design an electric hot air blower unit mounted adjacent to the freezer coils and allow the impingement of this hot air to melt off the excess ice.  The trouble with this is you are melting off the ice from the outside in; this can be a long and slow process, during which it is extremely difficult to stop this hot air from percolating into the cabinet interior and substantially raising its internal temperature.

This was the reason our cabinets were failing.  During defrost cycles the top two shelves in the cabinets were hopelessly out of specification (actual – 14^oC required -25^oC).  The answer was to redesign the defrost methodology.  During the defrost cycle we circulated the hot gas coming from the compressors through the heat exchange.  This sudden flow of hot gas quickly broke the bond between metal parts and the encumbering ice.   This bond being broken the ice dropped down in to the splash tray below.

This allowed the defrost cycle to be reset to much shorter intervals. This in turn kept the heat exchanger relatively clear from heavy icing conditions and so significantly enhanced it's thermal efficient while enabling the defrost cycle duration to be reset from seventeen minutes (pre-redesign) to less than six minutes (post redesign).  Since there was now no defrost hot air being circulated the impact of this new defrost methodology on the cabinet internal temperature was found to be insignificant.   The electrical power consumption for each modified cabinet dropped by 31%. 

Bottom of Form

Climatic Zone Validation Package-2 (Issue 3)
$2575.00
10000398

This package is complete with all the validation documentation you require to validate the climatic condition within a warehouse a room or a large cabinet. Documentation includes our interactive and detailed Validation Plan (VP) the Validation Risk Assessment (VRA) the really easy to use Installation Qualification (IQ), the Operational Qualification (OQ) and finally the Performance Qualification (PQ). Along with the documentation are 10 highly accurate and easy to use data loggers ready to monitor and record close to 17K (each) parameters over what ever time base you select. This is now the simplest most expedient and most cost effective method of validating the climatic condition within any climatically controlled zone.
Includes VP, VRA, IQ, OQ & PQ. Along with 20 RH & Temp EL-USB-2 data loggers.

Bottom of Form

Climatic Zone Validation Package-1 (Issue 1)
$1525.00
10000399

This package is complete with all the validation documentation you require to validate the climatic condition within a warehouse a room or a large cabinet. Documentation includes our interactive and detailed Validation Plan (VP) the Validation Risk Assessment (VRA) the really easy to use Installation Qualification (IQ), the Operational Qualification (OQ) and finally the Performance Qualification (PQ). Along with the documentation are 10 highly accurate and easy to use data loggers ready to monitor and record close to 17K (each) parameters over what ever time base you select. This is now the simplest most expedient and most cost effective method of validating the climatic condition within any climatically controlled zone.
Includes VP, VRA, IQ, OQ & PQ. Along with 10 RH & Temp EL-USB-2 data loggers.

Combination IQ/OQ/PQ Protocol.
This combination protocol has been produced in response to several hundred reader suggestions we received in our - Suggestions Section. It has been carefully designed to make it the preferred choice for Process and Laboratory stand-alone equipment. It is an interactive, fully detailed, sixty three page protocol that runs to approximately seven thousand words. It is presented in 'MS Word' to facilitate ease of final editing by the end user. It has become a very popular document.