Located near the North Yorkshire village of Holmefirth, UK, Longley Farm has been owned by the Dickinson family since 1948 when brothers Joseph and Edgar inherited their great uncle’s farm and 10 cows. In 1956, they began making their own cream, which evolved into investing in a herd of Jersey breed cows.
“The reason we went into Jerseys is because they produce the highest quality milk in protein and butterfat,” says Joseph. “We found you could make Jersey milk straight into very good yogurt without adding other ingredients.”
Today, the farm boasts what is said to be one of the best quality Jersey cow herds in the UK and tops up demand with milk from up to 40 farmers around the UK. The milk is used in its range of dairy products, including butter, cream, buttermilk, yogurt, cottage cheese, crème fraîche, sour cream and fromage frais. The farm also makes its own ice cream, together with the specialty Yorkshire Curd.
All of Longley Farm’s products are made without the use of artificial additives, colorings, preservatives or stabilizers, and are sold in local shops and UK supermarkets.
The need for heat exchangers
Like most dairies, the 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 that produces fresh cream and Yorkshire Curd have experienced new corrugated tube-type heat exchangers. 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 more economical, improving process efficiencies by re-using heat and helping 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 [that] are integral to our operation in a number of ways,” says Konrad Schwoch, operations and technical manager. “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 heat exchangers from HRS Heat Exchangers, Marietta, Ga., 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,” says Schwoch. “That was the main reason for using a tubular heat exchanger, as it is gentler on the cream and improves product quality.”
For example, if you “beat up” cream 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, also facilitating 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.
“We buy equipment that we hope is going to last,” adds Schwoch. “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 real 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.
“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,” says Schwoch. “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 selected to improve Yorkshire Curd production is a different design than that used for cream. This time a corrugated tube design, which specifically increases turbulence, was chosen to help 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.
“Using this traditional method creates a problem when you want to heat or cool the solution,” Schwoch says. “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 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,” adds Schwoch.
Because the unit will not need unblocking, together with its robust design and ease of servicing, means 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 meters above the factory floor.
Energy recovery
A further benefit of the HRS heat exchangers is the 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,” says Schwoch. “While it adds another level of complexity to the overall process, in some places we want to heat products and in other places cool them again, so efficiency is very important overall. 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 relative complex process compared to some other situations, so we need to work with a company that 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.”
