COMPACT CO 2 /NH 3 REFRIGERATION UNIT FOR THE COLD STORAGE

Transcription

1 COMPACT CO 2 /NH 3 REFRIGERATION UNIT FOR THE COLD STORAGE WITH USEING CO 2 FORCED CIRCULATION SYSTEM TOYO ENGINEERING WORKS.LTD C-dig meeting : 28 August

2 In the first half, I introduce a compact CO2/NH3 refrigeration unit for the cold storage. In the second half, I introduce a cold storage exhibition system of the mammoth in the Aichi world exhibition, although it is not in agenda. TOYO ENGINEERING WORKS.LTD 1

3 Introduction We have constructed many cold storage warehouse with a small water cooled condensing unit "LTS" in Japan from 25 years ago. Refrigerant of this unit is the HCFC-22. Like this, we have delivered many LTS. Therefore, it is necessary that shall be renewal the aged LTS and also HCFC refrigerant. We think it is necessary to diffuse the natural refrigerant system for earth environment. Therefore, we developed CO2/NH3 circulation system "C- LTS". The development point in the renewal is to make the unit compactly. 3

4 Example that Used the LTS Unit This example shows the LTS unit at the outside of a cold storage warehouse of every floor. Water Cooling Tower Cold Storage Warehouse LTS Unit The system is a direct expansion refrigeration of the HCFC-22. The cold room temperature is the range of minus 30 degrees from minus 5 degrees. There are many LTS unit in one cold storage warehouse, because a small unit needs no maintenance person in law. We delivered about 5,000 units in Japan. 4

5 Example that Used the LTS Unit This example shows one LTS unit in the upper side vacancy of the freezing room entrance. LTS Unit Cold Room 5

6 Example that Used the LTS Unit This example shows the plural LTS unit in a machine room. LTS Unit 6

7 Series of Compact C-LTS Models 220F-WP 370F-WP 550F-WP Cooling Capacity [kw] 32 / / / 87 Shaft Power [kw] 20 / / / 51 Power Supply Refrigerant Comp. Type Motor Rated Power [kw] AC 3φ 200V 50/60 Hz NH3/CO2(Secondary / Refrigerant) Open type Two-stage Screw CO2 pump [kw] Size : W L H [m] Weight [kg] 2,600 3,700 4,000 7

8 Schematic diagram of system flow NH3 Compressor C-LTS UNIT CO2/NH3 System Flow Sheet NH3 Condenser Cascade Condenser NH3 Receiver CO2 Receiver Evaporator Expansion Valve CO2 Pump 1 38

9 Outside Photograph of Compact C-LTC New model 9

10 Cascade condenser Inside of Compact C-LTC CO 2 Receiver NH 3 Condenser NH 3 Compressor NH 3 Receiver 10

11 Cascade condenser CO2 liquid outlet CO 2 Receiver NPSH=800mm NPSH : Net positive suction head CO 2 Liquid pump 11

12 We make Compact C-LTS smaller than prototype CO2/NH3 unit. Prototype CO2/NH3 circulation unit 40% Volume Decrease New Compact C-LTS New model 1.9m 3.8m 3.5mH3.5mH 1.5m 2.5m 1.9mH As a result, the size of compact C-LTS became equal with the old HCFC-LTS. 12

13 Method for Downsizing /Adoption of a CO2 Subcooling System A CO2 Subcooling System has the biggest effect for downsizing. The CO2 liquid of the receiver is cooled by the evaporation of NH3. The purpose of subcooling is to make NPSH of the CO2 liquid pump smaller. (NPSH : Net positive suction head) In this way, we can reduce the height of the unit. The NPSH of the CO2 liquid pump is 1.4 m. The subcooling degree of 1K is equal to NPSH of about 3.5 m. The subcooling of the CO2 liquid is effective to "the reduction of necessary NPSH" and "the downsizing of the unit". 13

14 The example of the operation condition without subcooling (1) C ooler w ind C ooler tem perature e Electric current value of C O 2 liquid pum p 15 Cooler air temperature Current value of CO 2 liquid pump Cavitation 10 5 liquid 2 Electric currunt value of C O pum p A Tim e m in Relationship Electric current value of C O 2 liquid pum p to cooler tem perature (N o super cooling) 14

15 The example of the operation condition with subcooling (a) C ooler tem peratu re Cooler air temperature Current value of CO 2 liquid pump C ooler w ind Tim e,m in Electric current value of C O 2 liquid pum p Stable driving liqu id 2 E lectric c urre nt value of C O pu m p A Relationship Electric current value of C O 2 liquid pum p and cooler w ind tem perature (Super cooling) 15

16 Characteristic of Compact C-LTS We use the natural refrigerant (CO2 and NH3) that defends earth environment /ODP is a zero and GWP is 1 or less. We can renewal from HCFC-LTS to C-LTS with a compact design. 3. We can keep highly safe by supplying CO2 to a load side and minimum charge of NH3 in the unit. 4. Comparison with a brine (Ex. Ethylene glycol) system by NH3 cooling 1) Pump power is smaller/because it uses the latent heat of CO2 2) Brine control is unnecessary 16