Falling Film Chiller

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. Especially Ice water (near 0°C) has a very good heat capacity, i.e. by contrast with other cooling agents, relatively small quantities can convey a large amount of heat.

What makes the falling-film chiller so interesting is its relatively simple and relieble operation including a high cooling performance to represent the ideal industrial water chiller. Water flows down the vertical plates. It is an open system that is accessible for cleaning, even during operation. Completly made out of stainless steel.

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.

What’s a Falling Film Chiller?

How does a Falling Film Chiller work?

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 highest possible outside film coefficient. By highest descent speed, highest U transmission coefficients are reached.

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. 

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.

Low-specific and thermodynamic parameters from an industrial water chiller 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.

Why a Water Chiller?

Furthermore water near freezing point at 0.5°C is 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. There are no additional costs for planning, piping, mounting of the valves and eletric wiring, as well as setting and programming of controllers, like known with Plate-Heat-Exchangers. No gaskets.

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.

Industrial Applications for Industrial Water Chillers

What’s the Process?

In the Falling Film Chiller or baudelot industrial water chiller 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.

Our devices generate a maximum power reserve in production with this baudelot ice water cooler at this temperature. Different from Plate-Heat-Exchangers, there is no need of temperature control, hot gas-defrost or flow control on water side. Costs for controller and temperature sensor do nor depend on the capacity. Control valves and pilot valves as well as solenoid valves and additionl shut valves are dempendent on capacity.

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.

De-oiling device of an industrial water chiller

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 helpful 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.