制冷系统
一、制冷原理与循环 | Refrigeration Principles & Cycle
二、压缩机类型 | Compressor Types
三、制冷剂与环保 | Refrigerants & Environment
四、冷却水与冷却塔 | Cooling Water & Cooling Towers
Ammonia Refrigeration System Safety Review — Cold Storage Facility
We're building a 20,000 m² cold storage warehouse with three temperature zones: -25°C deep freeze, 0°C chill, and 10°C dock area. Total cooling load is roughly 2,800 kW. Lars, what's the refrigeration system design?
我们在建一个2万平米冷库、三个温度区：-25°C速冻、0°C冷藏、 10°C卸货区。总冷负荷约2,800 kW。Lars，制冷系统怎么设计的？
For this capacity, ammonia is the clear winner. We're proposing a two-stage ammonia system with screw compressors. Ammonia — R-717 — has zero ODP and zero GWP. It's a natural refrigerant. The COP at -25°C evaporation and 35°C condensing is about 2.1 — versus about 1.6 for an equivalent R-134a system. Over 20 years, the energy savings alone will be over $600,000 compared to synthetic refrigerants.
对这个容量，氨是不二之选。我们建议双级氨系统配螺杆压缩机。氨—— R-717——ODP和GWP都为零。是天然制冷剂。-25°C蒸发/35°C冷凝时COP 约2.1——相对等效R-134a系统约1.6。20年下来，仅省的电费就能超过 60万美元对比合成制冷剂。
Ammonia is toxic and flammable — that's a serious safety concern. What safeguards are you putting in place? I need to know this system won't endanger the workers.
氨是有毒可燃的——这是重要的安全关切。你们设了什么防护措施？我 需要知道这个系统不会危及工人。
Absolutely, Maria. Here's our safety design: first, the ammonia charge is limited to 1,800 kg — we use a secondary refrigerant (glycol) loop for the distribution to the cold rooms, so the ammonia stays in the machine room only. Second, the machine room has ammonia gas detectors — 8 sensors at strategic locations. At 25 ppm, a ventilation alarm activates. At 150 ppm, the system goes into emergency shutdown — compressors stop, liquid isolation valves close. Third, the machine room has explosion-proof electrical classification per ATEX zone 2. Fourth, emergency ventilation — 30 air changes per hour, activated automatically. And every worker in the facility gets ammonia safety training plus SCBA equipment on site.
当然，Maria。我们的安全设计：第一，氨充注量控制在1,800 kg——使用 二次冷媒（乙二醇）回路分配到冷间，氨仅留在机房内。第二，机房配备氨 气检测器——8个传感器在关键位置。25 ppm时通风报警启动。150 ppm时系统 紧急停机——压缩机停、液体隔离阀关。第三，机房电气按ATEX 2区防爆 分类。第四，应急通风——每小时30次换气、自动启动。还有每名员工接受 氨安全培训、现场配空呼设备。
Lars, what about the oil management? Ammonia and oil don't mix well. In a screw compressor, oil carryover can be a problem, especially at low temperatures.
Lars，油管理呢？氨和油不太混合。螺杆压缩机里，跑油可能出问题， 特别是低温工况。
We're using polyalphaolefin (PAO) synthetic oil — it has better low-temperature fluidity than mineral oil. The system has high-efficiency oil separators on each compressor discharge — coalescing type, 99.9% efficiency. Plus oil coolers and oil return systems from the evaporator. We've got redundant oil pumps and a backup oil reservoir. Oil management on this system is very mature — we've installed 14 similar ammonia plants with zero oil-related failures.
我们使用聚α烯烃（PAO）合成油——低温流动性比矿物油好。每台压缩 机出口配高效油分离器——聚结式、99.9%效率。加油冷却器和蒸发器回油 系统。还有冗余油泵和备用油箱。这个系统的油管理很成熟——我们装了 14套类似氨系统、零油相关故障。
I want to see a written PHA — Process Hazard Analysis — before we approve this. And an emergency response drill before startup. If those check out, I'll sign off.
我要看到书面的PHA——工艺危害分析——才批准。还有启动前应急演练。 这些通过的话，我签字。