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HVACR318 – Refrigeration II

HVACR318 – Refrigeration II. Ice Machines, General Information. Ice Machine Overview. All Ice Machines are Rated in pounds per hour. Over 30 Manufacturers of Ice Machines Each has their own unique design features. Ice Appearance. Main selling points.

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HVACR318 – Refrigeration II

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  1. HVACR318 – Refrigeration II Ice Machines, General Information

  2. Ice Machine Overview • All Ice Machines are Rated in pounds per hour. • Over 30 Manufacturers of Ice Machines • Each has their own unique design features.

  3. Ice Appearance

  4. Main selling points • There are two main selling points when it comes to ice machines; they are: • Purity • Clarity • These qualities are achieved by continuous pumping of water over the face of evaporator, which • Keeps air from being trapped; and • Keeps suspended solids from adhering to the ice.

  5. Purity and Clarity • This differs from home refrigeration cubes, where water does not move and air bubbles cause cloudy cubes, along with unpleasant smell and taste.

  6. Ice Machine System • Each manufacturer produces one of two types of ice: • Cubed • Flaked

  7. Ice Cube Machines • Cuber water circuit - All cubers circulate water over the face of an evaporator using a water pump. • The temperature of this evaporator is below freezing. • Some of the water turns into ice and remains on the evaporator surface. • The rest falls back into the sump where it is re-circulated back to the evaporator. • The water pump is in constant operation while the ice is being formed.

  8. Ice Cube Machines • Cuber water circuit, cont’d: • Plastic or tygon tubing carries water over the entire face of the evaporator • A means of distributing the water over the entire face of the evaporator is required. • Stationary spread bar • Oscillating bar • Rotating or agitating bar • Small diameter holes

  9. Ice Cube Machines

  10. Ice Cube Machines • Types of harvest • Hot gas (most common) • Hot water bath • Electric (very rare)

  11. Ice Cube Machines • Harvest initiation types • Pressure • Temperature • Switching Arrangement • Probe switch • Timer Cams • A fixed number of cubes is made during each cycle (e.g., 60 or 120 cubes, etc.)

  12. Ice Cube Machines • Most cubers drain remaining water via the sump at the end of each cube batch. • Remaining water consists of suspended solids and impurities. • Water is drained and new water replaces it. • If this is not done, mineral content will build up and clog water passages.

  13. Ice Cube Machines • Most machines will have a mechanism for draining impurities at the end of each cube batch. For example, Crystal Tip dumps and flushes the entire system. • Most cubers will also cycle off the circulating pump during harvest cycle (e.g., Crystal Tip).

  14. Ice Flake Machines • Flakers are more limited in design • Drum is submerged in water. • Inside of drum acts as an evaporator. • A film of ice forms on its surface. • The film is continuously scraped by an auger. • Ice is pushed or compressed out of the drum by the auger. • Ice then falls into the bin. • This machine runs continuously (no harvest cycle) until the thermostat opens.

  15. Ice Flake Machine

  16. Ice Flake Machines • Flaker water circuit • Water is held in a reservoir above the drum. • Float valve mechanism maintains the water level in the reservoir. • Water flows by gravity to the lower portion of the drum.

  17. Ice Flake Machines • Flaker water circuit, Cont’d: • Auger turns approximately 25 rpm inside the drum (this is done with a motor and a reduction gear coupled to the end of the shaft). • Auger picks up water while turning. • Water is dispersed over the inside face of the drum and turns to ice.

  18. Ice Flake Machines • Flaker water circuit, Cont’d: • As the auger turns, it scrapes the ice off the inside of the drum. • The shape of the auger lobes carries the ice to the upper portion of the drum. • Ice is compressed through a small opening where it is directed down a chute and into a bin. • As the float in the reservoir drops, the water level is made up with fresh water.

  19. Ice Flake Machines • Flaker Ice, Purity and Clarity • Ice is cloudy, not clear. • Can have traces of discoloration • Can have odors • Can sometimes have bad taste

  20. Ice Flaker Machines • Flaker Ice Purity and Clarity, Cont’d: • These traits are associated with the condition of the supply water, and the rate of water movement through the evaporator. Solids remain suspended and air is trapped. • For these reasons, filters and softeners are often used in the water supply lines of flaked ice that is used in drinks.

  21. Ice Machine Circuits • All ice machines have three circuits: • Refrigeration Circuit • Water Circuit • Electrical Circuit

  22. Refrigeration Circuit • The refrigeration circuit • Same as most other circuits. • Major differences are: • The shape of the evaporator determines the shape of the cubes. Evaporator Types include: • Flat Plates (Inclined or tilted) • Upside down cubes (shot glasses) • Cylinder shaped • Embossed spots

  23. Refrigeration Circuit • Ice machines use a standard condensing unit that you would find on other low temperature systems. • Flow controls can be: • TXV • Capillary Tubes • AXV (Flakers only)

  24. Refrigerant Pressures • Low side pressures generally correspond to a 15 to 20 degree evaporator temperature. • When the water is warm, the pressures are high. • As ice builds up, the pressures gradually drop into design range. • Example: R12 = about 5 degrees.

  25. Refrigerant Pressures • Setting of the superheat should only be done when ice has begun to form on the evaporator. • Harvest cycles are short: 5 to 10 minutes. • Freeze cycles can be as long as an hour for large capacity, or 20 to 30 minutes for small capacity.

  26. Newer Refrigerants • Refrigerants are slowly changing: • R12 (most older machines – need to use drop in replacement) • R502 (high capacity) • R22 (Some split and newer machines)

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