Ice rink brine temperature? for ambient temperature above the ice surface +24°С

[aykut]

Hi, This is Aykut. I have a question about ice rink design.

Our Ice Rink Technical specification ;

-size of the ice rink; 806m2
-ambient temperature above the ice surface;+24°С
- relative humidity above the ice surface;50%
- air velocity above the ice surface;0,2m/sec
- ice thickness;40mm
- required cooling capacity;≈280kW
Refrigerant;R-404A
Outdoor Temperature;+40°С

We have two offer and two different disegn;

First offer;

Semi hermetic screw compressors (2+1) 1pcs.
- type Bitzer or similar

- cooling capacity 291,0kW
- evaporating temperature -17°С
- condensing temperature +50°С
- power consumption 224,0kW

Pipe & tube heat exchanger 1pcs.
- type Alfa-Laval or similar

- capacity 460,0kW
- evaporating temperature -17°С
- glycol inlet temperature -9°С
- glycol outlet temperature -12°С
number of circuits 3pcs

Second offer;

Semi hermetic screw compressors (3+1) 1pcs.
- type Bitzer or similar
- cooling capacity 282,0kW
- evaporating temperature -22°С
- condensing temperature +50°С
- power consumption 200,0kW

Pipe & tube heat exchanger 1pcs.
- type Alfa-Laval or similar
- capacity 320,0kW
- evaporating temperature -22°С
- glycol inlet temperature -14°С
- glycol outlet temperature -17°С

Which glycol inlet&outlet temperature true? (-9°С /-12°С or -14°С /-17°С)

[mbc]

first one better than second one
less compressor - more capacity in heat exchanger but ask them to reduce his design to -14°С /-17°С to get
better ice and hard ice with less time during ice up time.look like they have to change model of compressor

you asked . Which glycol inlet&outlet temperature true? (-9°С /-12°С or -14°С /-17°С)
both is true only design is different and delta T is same (3)

[aykut]

thanks for answer but i have doubt about ice temprerature for ambient +24°С

if glycol inlet&outlet temperature -9°С /-12°С then ice temperature will be +1,16°С
if glycol inlet&outlet temperature -14°С /-17°С then ice temperature will be -4С(it s true)

according to ice temperature formulas;

tm = ta – ((ta – ti) / Θ))

• tm – cooling medium temperature (°C); (glycol outlet temperature)
• ta – ambient air temperature (°C);
• ti – ice temperature (°C);
• Θ – ice layer relative (it is only coefficient)

Θ=2•π•λc/(ε•α•ln((2•ε)/(π•d)•sh(2•π•(h+λc/α)/ε)))

• ε – distance between pipe loops (m);
• α – heat-transfer factor W/m2•K;
• h – equivalent heat resistance layer;
• d – pipe diameter (m);
• λc - concrete heat conductivity (W/m•K).
• sh – hyper sinus

α=(Q-q)/(ta-ti)

• Q – total heat load (kW);
• q – heat load through the ground (kW).

h=d/2+δc+δi•(λc/λi)

• δc – concrete layer thickness above the pipe loops (m);
• δi – ice layer thickness (m);
• λi - ice heat conductivity (W/m•K).

• ta = +24°C, customer request;
• ti = - 4°C, customer request;
• ε = 0.08m, ice rink standard solution;
• d = 0.025m, ice rink standard solution;
• λc = 1.75W/m•K, physical properties tables;
• λi = 2.21W/m•K, physical properties tables;
• Q = 264.64kW, taken from HUURRE calculation;
• q = 6.53kW. not mentioned in HUURRE calculation so i use 8.1W/m2;
• δc = 0.032m, ice rink standard solution;
• δi = 0.04m, customer request.

[MilosBog]

one question, why haven you you used method of heat resistances with heat source? And coudl you tell me where have you found this formula? could you post a link or anything else which will give a bit better understanding of physics behind.
BR
MilosBog