Falling Film Chiller Process reliability to produce constant cooling of ice water near freezing point
Falling Film Chiller or so-called baudelot ice water cooler are mainly designed for cooling water down to 0.5°C near freezing point. In order to avoid building of ice at the panels, the suction gas pressure at the evaporator suction header has to be regulated. To keep the evaporation temperature not lower than the designed one, e. g. -3°C, as well as the water temperatures and flow. At systems used with e. g. glycole inside, the glycol inlet temperature has to be controlled.
Especially Ice water has a very good heat capacity, i.e. by contrast with other cooling agents, relatively small quantities can convey a large amount of heat. In particular, achieve high cooling performance. The flow-specific and thermodynamic parameters of water are favorable, so that high heat transfer rates can be achieved. However, the freezing point of the water itself (zero point) sets crucial physical boundaries for ice water production and cooling with ice water. Above all, temperatures achievable in the water are made to approach the zero point as closely as possible in order to exploit maximum temperature differences for the products to be chilled with ice water and to keep the temperature of the cooled product as low as possible.
Low-specific and thermodynamic parameters of ice water near freezing point
As zero point is approached, the problems in ice water production with the attendant risk of ice formation increase. The known anomaly of water (lowest specific volume at 4°C) results in the water volume expanding when it freezes, and under certain circumstances this can cause destruction of the equipment used. Furthermore, ice formation in ice water systems with their thick layers of ice always involves considerable performance losses because the ice layer acts like insulation and greatly reduces the thermal transmission output.
Consequently ice water production calls for a technique that on the one hand brings the water temperature as close as possible to zero point, but on the other hand is not susceptible to potential ice formation. If control fluctuations of the cooling system lead to ice formation, a layer of ice on the panels will reduce the heat transfer and reduce the cooling power of the baudelot ice water cooler. Building of ice at the panels may occur for some minutes, but there will not follow any mechanical destruction as in Plate Heat Exchangers. Ice will melt automatically after raising of the temperature inside the panels within the next normal operation mode cycle. Our devices generate a maximum power reserve in production with this baudelot ice water cooler at this temperature.
Falling Film Chiller Method of operation
The Falling Film Chiller or so-called baudelot ice water cooler consists of a distribution tray for the water at the top, a heat exchange system, a frame and a cover and a bottom collecting tank for water (optional). Water is pumped into the distribution tray and at a controlled rate is distributed homogeneously by a distribution through onto vertical panels in an open system.
The process water flows in a thin film over the outer surface down on the panels and obtains the highets possible outside film coefficient. By highest descent speed, highest U transmission coefficients are reached.
A high flow velocity ensures highly efficient heat transfer and a kind of a helpful self cleaning effect, which allows the operation with polluted liquids as well. Completely made out of stainless steel, it assures all required sanitary requirements, as the Ice water is always in contact with stainless steel parts AISI 304 or 316L or higher stainless steel grades up to titanium.
Ice water in dairy processes
A Falling Film Chiller or baudelot ice water cooler continuously generates ice water at 0.5 ° C without ice formation. Ice water is the ideal cooling medium for milk-processing plants, because it is non-toxic, has excellent heat transfer and transport properties, is inexpensive and available everywhere. To meet high global quality standards, fast and smooth cooling processes must be guaranteed from processing to storage of sensitive dairy products such as milk, milk powder, yoghurt, milk desserts, butter and cheese, mostly at the expense of high energy costs.
Milk processing plants are therefor looking for partners such as Heat Transfer Technology AG in order to realize saving potentials in the field of ice water technology. In order to expand the capacity of a dairy, operators often install additional ice water storage tanks. This is associated with high financial cost and space requirements. A corresponding alternative is the use of a Falling Film Chiller for ice water pre-cooling. In addition to the robust, simple operation and high energy efficiency, the advantages are that ice water temperatures between 0°C and 1°C can be generated without risk. Falling-Film Chiller cool the returning water, before it enters the ice water storage tank, thus relieving the existing plant.
Ice water in food processes
Furthermore water near freezing point at 0.5°Cis an important part in food refrigeration, to ensure the fastest possible cooling of the product due to the best possible product quality. The open, non-pressurized water side of this Falling Film Chiller or baudelot ice water cooler allows inspections and cleaning of dirt without disassembly in a few minutes.
Most noteworthy Ice water at 0.5°C can cool large produce in very short period of time. Similarly blanching, cooling and washing processes are mainly focussed as well as mixing processes with any requirement of low temperatures while or right after mixing processes. There are various detailed sanitary adjustments for the standard Falling Film Chiller due to different process requirements in use. But the appropriate adaptation can be just as good, as the information, given by the customer, concerning the application on site.
Falling Film Chiller general fields of applications
In the Falling Film Chiller or baudelot ice water cooler the homogeneous falling film allows to chill water down to 0,5 °C. Within industrial processes it can function as pre-chiller for industrial ice bank systems or is connected to the ice water side of a Plate Heat Exchanger. Or will be pumped directly to various food cooling processes. From the water collecting tank under the Falling Film Chiller pumps to bring the chilled water to the desired consumption locations.
Process water with discontinuous inlet water flow
If water with discontinuous or changing flow rate temperatures is to be cooled, there is a split-tank-design, which allows continuous operation of the evaporator, what is aspired for any refrigeration machine. The water reservoir with flow path is individually designed according to the flow profile and the water temperatures. This Falling Film Chiller or baudelot ice water cooler is designed to be robust to unexpected fluctuations in operation. Due to the exclusive processing of stainless steel, we meet all the requirements for a food-grade design of an Ice Water Falling Film Chiller.
Why mainly NH3 ?
The natural refrigerant ammonia, which is not only climate-neutral, but also highly energy-efficient, is normally used. Due to its very good thermodynamic properties, ammonia requires the least amount of energy to generate a certain cooling capacity.
This advantage is particularly important in dairies with their large plants, so that refrigeration plants using ammonia have proven their worth in the milk processing industry. At the same time the ammonia volume in this system is low. Gravity-driven evaporators with separators are used. In this way, the efficiency of the system is increased compared to plants with direct expansion and energy costs are reduced. For heat recovery, effective systems use an evaporative condenser, a heater and oil cooler. All in all, this increases the efficiency of the entire system an reduces operating costs.
If the Falling Film Chiller is used with NH3, a de-oiling device for the system is provided as a small
suction pipe at the liquid bottom header of the system for gravity or pump operation. This is standard
for NH3 and done on request for CO2. With refrigerant NH3, and depending on the oil, probably as well for CO2, there are severe miscibility gaps or solubility gaps with different oils, even if helpfull additives are used. Prior to the de-oiling procedure the evaporator system must be out of operation for some time, to allow the oil to separate to the bottom of the system.
In case of using oil with a lower density compared to the liquid refrigerant CO2, the refrigerant has to
be evaporated completely for this de-oiling function. A regular de-oiling is needed, according to the properties of the refrigerant compressor and the oil. Experienced engineers with academic advice are responsible for the design. Individual channel design and construction for each project due to the high inside film coefficient and low pressure drop.
The Baudelot cooler – Historical review and beginnings
Jean Louis Baudelot (1797–1881), was born in France, and studied engineering in Belgium. Though he claimed several inventions, fame came in 1856, when he patented a liquid cooler. Specifically intended for the brewing industry.
A cousin who was a brewer presented him with the fact that until then beer worts had to be cooled in a shallow vessel (cool ship) and stirred during a whole night—a process that easily took 8 hours. Worse, the continuous exposure of the worts to the air resulted often in unwanted inoculation and infected beer. Yet exposure was mandatory because beer yeasts need oxygen at the outset of fermentation. Therefore, the wort needs to be well aerated.
Baudelot envisaged a fine double copper sheet overlaying copper tubes (first cylindrical, later elliptical in cross-section) wherein cold water (spring water or icewater) ran countercurrent to the worts. The worts were collected on top of the cooler in shallow tray, and then finely dispersed, flowing over outside of the copper sheets, which were being being cooled internally. In this way, cooling took place in less than a quarter of the original time needed, limiting exposure to contaminating microbes, while aeration was assured. Hot wort flowed like an undulating waterfall down the exterior of the cooler, emerging cool and aerated at the bottom. It was a massive improvement that led to beer of much better quality and stability.
Falling Film Chiller advantages
- No risk of freezing with ice water of 0.5 ° C
- Low cost per kWh
- High efficiency, low pressure drop
- Suitable for contaminated liquids (for example greywater or red water)
- Easy access to the open system
- Easy to clean
- Cleaning during operation
- Low tendency to fouling
- No seals
- No destruction of the apparatus in case of ice formation
- Simplicity of control
- Enclosed design prevents product contamination
- Completely made of stainless steel, also for salt water
- Special falling film chiller versions possible
- Capacities from 10 kW to 10,000 kW
- Evaporator for all primary refrigerants (NH3, freonss, CO2) and operating modes. As well as secondary refrigerants (Any type of Glycol) or for brine operation
- All stainless steel materials, from AISI304 up to titanium, 254-SMO, Duplex etc.
This stainless steel execution gives assurance that the chilled water is always and only in contact with stainless steeel parts and can be used directly for the use required
- Plug-in units up to 100 kW, or for on-site refrigeration systems
Applications and benefits
- Evaporator for water cooling up to 0.5 ° C.
- Fastest cooling of food close to freezing by high efficiency
- No risk of freezing damage to food used in fresh produce, meat, fish, seafood etc.
- Falling Film Chiller are preferred in application of high capacities with limited ground space
- Falling Film Chiller plates chill liquids to almost refrigerant temperature
- Ideal for cooling down milk, yoghurt and cheese cooling. As well as for beer, meat, fish, vegetables and food and beverages in general
- “White Water” for the cooling of vacuum pumps in the pulp and paper industry
- Waste water from sewage treatment plants
- Waste water from process and chemical industry plants
- Cooling water in chemical and process industry
- Sea and river water in heat recovery plants
- CO2 evaporation in breweries and soft drink producers
- Comfortable access to the open system
- Easy to clean:
- open water distribution tray
- large discharge opening for the discharge of particles
- removable side panels
- open construction plate system
Falling Film Chiller construction and dimensions example
|TYPICAL DIMENSIONS, WITHOUT TANK||L (m)||B (m)||H (m)|
|System type A||2.0||2.1||2.0|
|System type B||3.8||2.5||2.0|