POST 01141E : FRONT-OPENING REFRIGERATORS

POST 01141E : FRONT-OPENING REFRIGERATORS Follow-up on Posts 01125E and 01133E 15 August 2007 _________________________________________________________________ This posting contains three contributions. The first is from John Lloyd from PATH. Then Dereje Ayalew explains his question further, using a table. Finally Alejo Bejemino from the Philippines, also with a table explains what in his opinion are differences between types of refrigerators, making some suggestions. __________________________________ Correct Dr Banerjee, and they often also have defrost systems that raise the internal temperature periodically. Most front opening refrigerator cabinets designed for the domestic market have a lower hold-over time than the chest freezer cabinets that are used to build ILRs. Front opening refrigerators that are purpose-built for vaccines and pharmaceuticals have more insulation and are designed without door shelves or vegetable trays. But these refrigerators are marketed to the industrial world health market and are many times more expensive than domestic refrigerators. Over the years, efforts have been made to design and test conversion kits for front opening domestic refrigerators to prolong their hold-over time, but these 'retro-fit' systems have proved to be cumbersome and have never reached the market as far as I know. The only proven way to prolong holdover time in front opening domestic refrigerators is to keep a permanent store of water-filled icepacks which help to cool vaccines in the refrigerator when the power fails. If purpose-built pharmaceutical refrigerators are purchased for use in the cold chain they should be tested first, but they are likely to meet the standards. Some domestic front opening refrigerators may also meet the standards, particularly for temperate climates, but they should be tested before they are purchased. John Lloyd PATH -------------------- Dear all I would like to thank you all for the comments you have given me. To make my points more clear I have made some elaborations. Let’s assume that we are in a clinic with a 24 hour reliable AC power supply. And we wanted to buy a refrigerator for this clinic. and we assume that we decide to buy a compression (AC) type refrigerator as it has a reliable 24 hour power supply. The next question will be which type of compression (AC) refrigerators, front or top opening. Now on the PIS , 2000, 1997 there are no refrigerators which are front opening and compression one. Below I have tried to show this on a table. SN Compression refrigerators Absorption refrigerators Solar (12/24 VDC) 230/110 AC Front opening Available (RFVB , NAPS etc) Not Available Available (SIBIR Top opening Available (BP, Dulas etc Available (Vest frost etc) Available (Electrolux RCW 42,50 etc) As can be seen from the above table it is only front opening compression type refrigerators which are missing. As far as I know compression type refrigerators are more efficient in terms of producing the cooling effect from solar and absorption ones. It is recommended on the PIS to use front opening absorption and solar refrigerators so why not compression ones. Regards Dereje WHO/ Ethiopia Logistician --------------------- Dear all, Please find table below summarizing my views regarding this posting on front-opening refrigerators. Based on my field experience, one of the most important factor to consider when choosing a refrigerator is the hold-over time of the unit. In most cases top-opening compression type unit has longer hold-over time than front-opening absorption type unit since it has provision for ice-lining. However, front-opening compression type unit can also be produced with provision for ice lining but this I believe will reduce the cold storage space capacity of the unit and will result to leakage of the ice lining when arranged in horizontal position. Table comparing the features of front and top-opening refrigerators Description Type of door openings Front opening Top opening 1.Ice lining No provision for ice lining. This results in short hold over time Has provision for ice lining that lengthens hold over time. 2.Air tight seal on the door Air tight seal is sometimes dependent on proper closing of the door, door gasket magnet and door lock. The weight of the door (due to its top design) and the door gasket magnet can seal the door tightly to block warm/cold air leakage in/out of the refrigerator. 3.Vaccine arrangement Refrigerator has several divisions/layers for each type of vaccines to be arranged and identified quickly. Vaccine loading and unloading is easily done and takes shorter time. There is no separator inside. Vaccine loading and unloading takes longer time resulting to warm air entering the unit. Warm air contains moisture that causes more frost developing on the cool evaporator surface. 4.Door design Usually has double door for each refrigerator and freezer compartments. This makes the refrigerator compartment sealed while opening the freezer compartment. Single door which exposes cooled vaccines to warm air. 5.Type of refrigeration system Absorption type Compression type 6.Floor space Less floor space required. More space required. Top opening compression type unit can be further improved by having the following features: 1. A door for each refrigerator and freezer compartment (unit with both refrigerator and freezer compartment). This will seal each compartment while the other door is opened. 2. At least six baskets arranged vertically for each type of vaccines. This will segregate each type of vaccines making it easy for loading and unloading of the refrigerator/freezer. 3. A transparent glass door to be able to read the temperature and view the vaccine contents without opening the door. Transparent glass door will reduce frequency of door opening thus maintaining the vaccine storage temperature and prevent warm moisture laden air to enter the compartment resulting to frost build up on the cooled evaporator surface. Hope these are useful. Alejo H. 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