Slurry ice is a phase changing

refrigerant A refrigerant is a working fluid used in the refrigeration cycle of air conditioning systems and heat pumps where in most cases they undergo a repeated phase transition from a liquid to a gas and back again. Refrigerants are heavily regulated ...

made up of millions of ice "micro-crystals" (typically 0.1 to 1 mm in diameter) formed and suspended within a solution of water and a freezing point depressant. Some compounds used in the field are

salt Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of salts; salt in the form of a natural crystalline mineral is known as rock salt or halite. Salt is present in vast quant ...

ethylene glycol Ethylene glycol ( IUPAC name: ethane-1,2-diol) is an organic compound (a vicinal diol) with the formula . It is mainly used for two purposes, as a raw material in the manufacture of polyester fibers and for antifreeze formulations. It is an o ...

propylene glycol Propylene glycol ( IUPAC name: propane-1,2-diol) is a viscous, colorless liquid, which is nearly odorless but possesses a faintly sweet taste. Its chemical formula is CH3CH(OH)CH2OH. Containing two alcohol groups, it is classed as a diol. It ...

alcohols In chemistry, an alcohol is a type of organic compound that carries at least one hydroxyl () functional group bound to a saturated carbon atom. The term ''alcohol'' originally referred to the primary alcohol ethanol (ethyl alcohol), which is ...

like isobutyl and

ethanol Ethanol (abbr. EtOH; also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound. It is an alcohol with the chemical formula . Its formula can be also written as or (an ethyl group linked to a ...

, and sugars like

sucrose Sucrose, a disaccharide, is a sugar composed of glucose and fructose subunits. It is produced naturally in plants and is the main constituent of white sugar. It has the molecular formula . For human consumption, sucrose is extracted and refine ...

and

glucose Glucose is a simple sugar with the molecular formula . Glucose is overall the most abundant monosaccharide, a subcategory of carbohydrates. Glucose is mainly made by plants and most algae during photosynthesis from water and carbon dioxide, u ...

. Slurry ice has greater

heat absorption Heat transfer is a discipline of thermal engineering that concerns the generation, use, conversion, and exchange of thermal energy (heat) between physical systems. Heat transfer is classified into various mechanisms, such as thermal conduction, ...

compared to single phase refrigerants like

brine Brine is a high-concentration solution of salt (NaCl) in water (H2O). In diverse contexts, ''brine'' may refer to the salt solutions ranging from about 3.5% (a typical concentration of seawater, on the lower end of that of solutions used for ...

, because the melting

enthalpy Enthalpy , a property of a thermodynamic system, is the sum of the system's internal energy and the product of its pressure and volume. It is a state function used in many measurements in chemical, biological, and physical systems at a constant ...

(

latent heat Latent heat (also known as latent energy or heat of transformation) is energy released or absorbed, by a body or a thermodynamic system, during a constant-temperature process — usually a first-order phase transition. Latent heat can be underst ...

) of the ice is also used. __TOC__

Characteristics

The small ice particle size results in greater

heat transfer Heat transfer is a discipline of thermal engineering that concerns the generation, use, conversion, and exchange of thermal energy ( heat) between physical systems. Heat transfer is classified into various mechanisms, such as thermal conducti ...

area than other types of ice for a given weight. It can be packed inside a container as dense as 700 kg/m³, the highest ice-packing factor among all usable industrial ice. The

spherical A sphere () is a geometrical object that is a three-dimensional analogue to a two-dimensional circle. A sphere is the set of points that are all at the same distance from a given point in three-dimensional space.. That given point is the ce ...

crystals have good flow properties, making them easy to distribute through conventional pumps and piping and over product in direct contact chilling applications, allowing them to flow into crevices and provide greater surface contact and faster cooling than other traditional forms of ice (flake, block, shell, etc.). Its flow properties, high cooling capacity and flexibility in application make a slurry ice system a substitute for conventional ice generators and

refrigeration The term refrigeration refers to the process of removing heat from an enclosed space or substance for the purpose of lowering the temperature.International Dictionary of Refrigeration, http://dictionary.iifiir.org/search.phpASHRAE Terminology, ht ...

systems, and offers improvements in energy efficiency: 70%, compared to around 45% in standard systems, lower

freon Freon ( ) is a registered trademark of the Chemours Company and generic descriptor for a number of halocarbon products. They are stable, nonflammable, low toxicity gases or liquids which have generally been used as refrigerants and as aerosol prope ...

consumption per ton of ice and lower operating costs.

Application fields

Slurry ice is commonly used in a wide range of

air conditioning Air conditioning, often abbreviated as A/C or AC, is the process of removing heat from an enclosed space to achieve a more comfortable interior environment (sometimes referred to as 'comfort cooling') and in some cases also strictly controlling ...

packaging Packaging is the science, art and technology of enclosing or protecting products for distribution, storage, sale, and use. Packaging also refers to the process of designing, evaluating, and producing packages. Packaging can be described as a c ...

, and industrial cooling processes, supermarkets, and cooling and storage of fish, produce, poultry and other perishable products. sunwell fish packing pumpable slurry ice

sunwell fish packing pumpable slurry ice

Slurry ice can boost by up to 200% the cooling efficiency of existing cooling or freezing brine systems without any major changes to the system (i.e.

heat exchanger A heat exchanger is a system used to transfer heat between a source and a working fluid. Heat exchangers are used in both cooling and heating processes. The fluids may be separated by a solid wall to prevent mixing or they may be in direct conta ...

, pipes, valves), and reduce the amount of

energy consumption Energy consumption is the amount of energy used. Biology In the body, energy consumption is part of energy homeostasis. It derived from food energy. Energy consumption in the body is a product of the basal metabolic rate and the physical activit ...

used for pumping.

Advantages

Slurry ice is also used in direct contact cooling of products in food processing applications in water resistant

shipping container A shipping container is a container with strength suitable to withstand shipment, storage, and handling. Shipping containers range from large reusable steel boxes used for intermodal shipments to the ubiquitous corrugated boxes. In the context of ...

s. It provides the following advantages: *Product is cooled faster – the smooth round shape of the small crystals ensures maximum surface area contact with the product and as a result, faster heat transfer. *Better product protection – the smooth, round crystals do not damage product, unlike other forms of sharp, jagged ice (flake, block, shell, etc.). *Even cooling – unlike other irregular shaped ice which mostly conducts heat through the air, the round shape of the slurry crystals enables them to flow freely around the entire product, filling all air pockets to uniformly maintain direct contact and the desired low temperature.

Slurry ice generators

Slurry ice is generated using a unique type of ice-making technology. Conventional ice generators produce sharp edged, dry ice fragments, not the small, spherical crystals found in slurry ice. In traditional brine chiller systems, crystals forming inside the solution would block or damage the system.

Scraped surface generators

The world’s first

patent A patent is a type of intellectual property that gives its owner the legal right to exclude others from making, using, or selling an invention for a limited period of time in exchange for publishing an enabling disclosure of the invention."A ...

for a slurry ice generator was filed by Sunwell Technologies Inc. of

Canada Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by to ...

in 1976. Sunwell Technologies Inc. introduced slurry ice under the trade name deepchill ice, in the late 1970s. Slurry ice is created through a process of forming spherical ice crystals within a liquid. The slurry ice generator is a scraped-surface vertical

shell and tube heat exchanger A shell and tube heat exchanger is a class of heat exchanger designs. It is the most common type of heat exchanger in oil refineries and other large chemical processes, and is suited for higher-pressure applications. As its name implies, this ty ...

. It consists of

concentric In geometry, two or more objects are said to be concentric, coaxal, or coaxial when they share the same center or axis. Circles, regular polygons and regular polyhedra, and spheres may be concentric to one another (sharing the same center p ...

tubes with refrigerant flowing between them and the water/freezing point depressant solution in the inner tube. The inner surface of the inner tube is wiped using a wiping mechanism which in the original Sunwell design consists of a central shaft, spring-loaded plastic

blade A blade is the portion of a tool, weapon, or machine with an edge that is designed to puncture, chop, slice or scrape surfaces or materials. Blades are typically made from materials that are harder than those they are to be used on. Histor ...

s, bearings and

seals Seals may refer to: * Pinniped, a diverse group of semi-aquatic marine mammals, many of which are commonly called seals, particularly: ** Earless seal, or "true seal" ** Fur seal * Seal (emblem), a device to impress an emblem, used as a means of a ...

. The small ice crystals formed in the solution near the tube surface are wiped away from the surface and mixed with unfrozen water, forming the slurry. Other slurry ice generators adapted the first idea of the scraped surface wiping the surface by using an

auger Auger may refer to: Engineering * Wood auger, a drill for making holes in wood (or in the ground) ** Auger bit, a drill bit * Auger conveyor, a device for moving material by means of a rotating helical flighting * Auger (platform), the world's f ...

originally designed to create flake ice. Wipers can be also brushes or

fluidized bed A fluidized bed is a physical phenomenon that occurs when a solid particulate substance (usually present in a holding vessel) is under the right conditions so that it behaves like a fluid. The usual way to achieve a fluidize bed is to pump pressur ...

heat exchanger for ice crystallization. In this heat exchangers steel particles circulate with the fluid mechanically removing the crystals from the surface. At the outlet steel particles and slurry ice are separated.

Direct contact generators

immiscible Miscibility () is the property of two substances to mix in all proportions (that is, to fully dissolve in each other at any concentration), forming a homogeneous mixture (a solution). The term is most often applied to liquids but also appli ...

primary refrigerant evaporates to supersaturate the water and form small smooth crystals. With direct contact chilling, there is no physical boundary between the brine and the refrigerant, increasing the rate of heat transfer. However, the major disadvantage of this system is that a small amount of refrigerant stays in the brine, trapped in the crystals. This refrigerant is pumped with the slurry out of the generator and into the environment.

Supercooling generators

Pure water is

supercooled Supercooling, also known as undercooling, is the process of lowering the temperature of a liquid or a gas below its melting point without it becoming a solid. It achieves this in the absence of a seed crystal or nucleus around which a crysta ...

in a chiller to −2°C and released through a nozzle into a storage tank. On release it undergoes a

phase transition In chemistry, thermodynamics, and other related fields, a phase transition (or phase change) is the physical process of transition between one state of a medium and another. Commonly the term is used to refer to changes among the basic states ...

forming small ice particles within 2.5% ice fraction. In the storage tank it is separated by the difference in density between ice and water. The cold water is supercooled and released again increasing the ice fraction in the storage tank. However a small crystal in the supercooled water or a nucleation cell on the surface may act as a seed for ice crystals and block the generator.

References

*Michael Kauffeld, Masahiro Kawaji, Peter W. Egolf. Handbook on Ice Slurries. IIR
Delft University of Technologies (NL)
{{fishing industry topics Refrigerants Food preservation Fish processing Water ice