Corrugated-tube heat exchangers benefit Yorkshire dairy
A UK-based dairy has improved production of its local delicacy, Yorkshire Curd, by installing two HRS corrugated tube heat exchangers.
Located near the picturesque North Yorkshire village of Holmefirth, Longley Farm is one of the UK’s primary producers of Yorkshire Curd. Originally developed by Yorkshire farmers as a tasty way of using up any curds left over from cheese making, the uncooked fresh curd product is the key ingredient in a traditional Yorkshire curd tart. Today, this sweet pastry-cased delicacy filled with currants and egg is often served as a cold treat or a warm dessert.
While most dairies make curds and whey by adding bacteria to the milk to turn the lactose into lactic acid and stimulate the proteins to stick together, for Yorkshire Curd production, Longley Farm adds acid directly to the milk.
However, this traditional method creates very small curds, which get mixed into the whey portion. Particulates form, and traditional plate heat exchangers can easily become blocked. For this reason Longley Farm has chosen corrugated tube heat exchangers from HRS as their design prevents fouling of the tube wall and maintains efficient performance.
The need for heat exchangers
Like most dairies, the Longley Farm factory operates a number of heat exchangers to remove the heat from processing and manufacturing its dairy products, which must be chilled for sale. Most of these are of a traditional plate design, which is fine for simple heating or cooling purposes, but recent upgrades to the machinery which produces fresh cream and Yorkshire Curd have seen new corrugated tube-type heat exchangers installed.
Although the initial capital costs of tubular heat exchangers are higher than the simpler plate alternative, over the course of their operational life they can prove to be much more economical, improving process efficiencies by re-using heat and helping to maintain the quality of the end product. These tubular units overcome some of the limitations of plate heat exchangers, such as the relatively high pump pressures required, while also reducing maintenance costs over the life of the unit.
“We have a number of HRS heat exchangers which are integral to our operation in a number of ways,” explained Longley Farm Operations & Technical Manager Konrad Schwoch. “We use what we would consider a standard heat exchanger for cooling processes, but we now have two more sophisticated systems from HRS.”
Benefits of corrugated tubes
The new HRS heat exchangers incorporate corrugated tubes which provide a number of advantages over flat plate or smooth tube types. The biggest advantage is that heat transfer is increased, particularly at higher flow rates, meaning that less heat transfer area is required, resulting in a shorter, more compact design, together with associated cost savings.
This also results in gentler handling of the product during the cooling phase, which is crucial for fresh cream production. “For a cream process we want the cooling profile to be very gentle and we want to agitate the cream as little as possible,” said Konrad. “That was the main reason for using a tubular heat exchanger as it is gentler on the cream and improves product quality.” As he points out, if you ‘beat up’ cream, for example by pumping it over and over, you make butter, which is specifically not what is required in this situation. Maintaining the ideal temperature of the cream throughout the process is also vital for maintaining the quality of the finished product, which also facilitates its handling in the factory.
Corrugated tube heat exchangers have a lower pumping requirement than other tube-type heat exchangers as their compact nature results in a lower pressure drop during the heat exchange process. This helps contribute to the long operational life and reduced maintenance of the unit, which has advantages for Longley Farm.
“We buy equipment that we hope is going to last,” commented Konrad. “Therefore the cost and downtime associated with maintenance is a key consideration. You want to make sure that you’ve bought something that is reliable, doesn’t need a lot of maintenance, isn’t hard to look after, is good value for money and lasts a long time. For me, the value in the tube-type heat exchanger is that it is a more robust piece of equipment. It’s harder to break and easier and cheaper to service, saving money over the lifespan of the unit.”
Like all HRS heat exchangers, the corrugated tube units are made from high-quality stainless steel which Konrad finds appealing: “Because of the innovation you get from HRS, such as multi-tubes and annular spaces, you have a lot more surface area than a traditional tubular heat exchanger. Because of this, and because they have a number of different designs and different applications, the actual size of the new system is smaller than the old equipment it is replacing, making it easier to incorporate into the factory layout.”
A different design is required for curd production
The new heat exchanger chosen to improve Yorkshire Curd production is a different design to that used for cream. This time a corrugated tube design which specifically increased turbulence was chosen to help to reduce fouling inside the tubes.
While most dairies make curds and whey by adding bacteria to the milk to turn the lactose into lactic acid and stimulate the proteins to stick together, for Yorkshire Curd production, Longley Farm adds acid directly to the milk, which is the traditional way of making the product.
“Using this traditional method creates a problem when you want to heat or cool the solution,” explained Konrad. “The curd can be very, very small, so when you are pumping it you get curd mixed into the whey portion. When you want to pump it you know you are going to get particulates in it, so we need to use a corrugated tube heat exchanger because traditional plate heat exchangers can easily become blocked with the small bits of curd. It’s much easier and cheaper to use a corrugated tube heat exchanger in the long run.”
This unit has been specifically designed by HRS to handle these particulates, even if they reach levels well in excess of those found in normal operation. “Even if things go wrong and there is a lot of curd in the system, which shouldn’t happen, the system won’t become blocked or get damaged,” added Konrad. This confidence that the unit will not need unblocking, together with its robust design and ease of servicing, mean that it is not necessary to access the new heat exchanger as frequently as its predecessor. Consequently it has been installed on a platform 3 m above the factory floor.
A further benefit of HRS heat exchangers is their energy-recovery capabilities. The heat recovered from the cooling process for the Yorkshire Curd is used to warm water which is then transferred to the farm cottages across the road from the factory. The warm water is used to provide heating and hot water to the cottages and, although this is the first time that such an energy efficient scheme has been implemented on the farm, it has been so successful that the new tube heat exchanger on the cream line will soon be connected to the system.
“There’s an advantage to us in recapturing this heat,” explained Konrad. “While it adds another level of complexity to the overall process, in some places we want to heat products and then in other places cool them again, so efficiency is very important overall.” He also praised the level of understanding that HRS has shown when it comes to Longley Farm’s complex requirements: “Although we cool our products with heat exchangers, we also need to use a chilled water system to take out the last bit of heat in order to reach the chilled temperature required by our finished products. That’s a relatively complex process compared to some other situations, so we need to work with a company that we know understands that and that we can trust to deliver.
“With all our different requirements, including heating and cooling, it can be difficult to automate quite a complex group of processes and not end up with the biggest, most complicated plant in the world. The clever thing has been keeping the heat exchanger solution simple while providing everything we need.”
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