ACR Journal

CMYK / .ai CMYK / .ai CMYK / .ai acrjournal.uk 31 REFRIGERATION the evaporator, increasing cycle times and energy cost, as well as uneven cooling. From a technical point of view, the space itself is the single most important factor. Left to its own devices, air will follow the path of least resistance, and so it needs to be actively managed to ensure the correct path. It’s good practice to take velocity readings throughout the room to identify any dead air spots or return air paths. Without this detailed insight, it becomes a question of guesswork. It’s common to see equipment not working eciently due to poor room design. A simple bae may be all that’s needed to improve the airflow path and make it work properly. Component selection Critically, it’s important to manage superheats and control suction return temperatures and pressures into the compressor. This calls for a maximum opening pressure device on the evaporator, which can be a suction pressure regulator, a MOP valve or an electronic expansion valve, all of which will eciently control superheat gain on the evaporator and therefore reduce strain on the condensing unit. This is the key to safe and ecient operation. The dimensions and materials of the packaging, and even the nature of the product itself, also play a part in the specification process. So, for example, products or packaging which is especially dense will make it harder to get cold air through it to extract heat. Similarly, certain foodstu…s, including cheese, fish and o…al, give o… ammonia which will quickly degrade aluminium rendering it useless. (This is especially the case in maggot farms incidentally, a surprisingly big sector dedicated to UK anglers). The choice here is to accept the damage and regularly replace the evaporator or invest in a more expensive – but durable – solution. This might include an electro-tinned copper coil or high grade (316) stainless steel evaporator with 40 per cent copper mix to accommodate heat transfer rates. The upfront costs may be higher, but the long-term return on investment balances this — a conversation worth having when specifying solutions. Refrigerant choice Another key consideration relates to F-gas legislation and the use of refrigerants which is forcing users to seek alternatives, including CO 2 . Because of the higher associated costs with maintaining the CO 2 plant, we find that most users prefer switching from high to lower GWP gases such as R448/449 and are starting to look at A2L options. These gases are readily available and o…er good eciency, so they represent the best value solution. But as with anything, it’s vital to undertake any conversions in line with the manufacturer’s instructions, not just to validate warranties and prolong service life but also to ensure food safety. If the system runs outside its envelope, the result could be failed equipment and failure to meet stringent food regulations. Finally, there’s the question of regular and ongoing maintenance. This should include coil cleaning, leak monitoring and an annual check on the evaporator temperature di…erence to ensure superheats are correctly set. For maximum eciency, pro-activity is strongly recommended here. While there are understandably budget pressures on food manufacturers which influence equipment and maintenance, the consequences of failure are also significant. With so little margin for error, it’s important to get things exactly right. A2L refrigerant pack