Lesson Learned

Lesson Learned

KEM RUSSELL, P.E

Sometimes it may be difficult to understand but we all have free agency to believe what we want. Some people believe the earth is flat. Some believe we never landed on the moon. I suppose there are people who believe those amazing photos from various robotic machines on Mars are fake too. The list goes on and on. One thing that some people don’t believe is happening is climate change. From my personal experience, I think climate change has and is happening.

Decades ago, while doing multi-day hikes or canoe trips with my family, we seldom heard of wildfires, at least nowhere near as many as we hear about or experience today. I do recall while we were doing a canoe trip down part of the Yukon River in the Yukon Territory we did experience the effects of a couple of wildfires.

One morning, we woke up and there was ash all over everything. Not too deep, but very noticeable.

Another time we pulled off the Yukon River to visit an ancient Indian village which was a designated historical site. This site was many miles from anything except wilderness, but since it was a designated historical site, men were there to prevent a fire from overrunning and potentially destroying the site. My wife and I walked through the site taking pictures while our kids went exploring. It was only a short time later before the helicopter that we had seen at the site took off and we looked up as it passed over our heads. Hands waving and faces pressed against the copter windows were our kids!

The pilot had asked the kids if they wanted a ride since he wasn’t doing anything at the time. What would you say? “Let’s go!” the kids replied and away they went for a short ride. Things like that don’t happen often, and likely not anymore.

Has the climate changed? At least from my perspective in looking over the last 60 years, yes it has. There are many more wildfires, there are many

more days when the temperature goes from “not too bad” to “hotter than …”, well you get the idea. Now during the summer multi-day hikes can be stopped due to wildfires closing trails. Things like this rarely happened a few decades ago.

The winters have changed too. I remember when we could get over 4 feet or more of snow. Now 6” to 10” is a lot, but this is very location dependent since the wind patterns seem to have gotten much more chaotic as the polar caps have sunk.

How does climate change relate to a lesson learned in refrigeration? Well, something happened this summer at a large ammonia cold storage facility that was very unusual, in fact, it had never happened before. It was caused by a lower-than-normal refrigeration load, and a now more normal, very hot day. Here is what happened:

Ambient daytime temperatures were around 105°F. This particular facility was nearly empty of last year’s products, so there was minimal refrigeration load. Due to the light load and the low relative humidity in the area, the operator was able to set his head pressure control to 120 psig (a little less than 73°F). All seemed to be working fine until he came in the next day and reviewed the historical data of the operation of the cold rooms still running.

The data showed that the room in the complex furthest from the machine room was not holding temperature and that the mechanical float switch controlling the liquid feed into the surge drum for that room was always calling for liquid feed.

The operator checked the liquid level in the high-pressure receiver (HPR), and it was more than enough to feed many rooms.

He then went up to the surge drum, which was located in a doghouse (penthouse, whatever you want to call it) above the building roof. At the surge drum, he could hear what sounded like vapor going through the make-up liquid solenoid. How could that be? There was a good solid supply of liquid leaving the HPR.

The distance to the surge drum from the HPR was over 600 feet, and the line size to this particular building was 2”, which was large enough to feed all the cold rooms in this particular complex when they were refrigerating, but now there was only one room cooling.

On further study of the historical data, the operator also noticed that during the night the room came back down to temperature and the operation of the liquid float was normal. It cycled ON and OFF as expected.

Here’s the theory of what we think was happening. Due to the reduced

How does climate change relate to a lesson learned in refrigeration? Well, something happened this summer at a large ammonia cold storage facility that was very unusual, in fact, it had never happened before.

LESSON

LEARNED?

refrigeration load, there was little call for liquid through the 2” line and so the liquid in the line was moving very slowly, much slower than ever before. Since the ambient temperature was hot and the ammonia in the line was about 72°F it was vaporizing and producing the gas that the operator heard going through the liquid solenoid valve.

The operator was able to get the room cooling during the day by raising the head pressure to 140 psig (about 81°F), which seemed to reduce the amount of liquid being vaporized enough so there was sufficient liquid ammonia getting to the surge drum for the actual room refrigeration load.

Another climate change impact has been noticed on some evaporator condenser operations, particularly on condenser operations located close to large bodies of water.

One very large processing and freezing facility located very near the ocean had been having more and more days of higher than normal operating head pressure. The condensers had been designed for the 1% wet bulb temperature taken from the most recent ASHRAE data. The condensers were well maintained and because this system operated in a vacuum there was a purger in operation.

After checking a number of factors: condenser coil condition, fan, and pump operation spray nozzle operation, purge solenoid operation, condenser circuit inlet, and outlet hand valve positions the refrigeration operators were still scratching their heads about what was going on. Then the ambient conditions were checked. As with a lot of locations, the temperature was higher than normal (I don’t think normal means what it used to anymore), the wet bulb was also higher than the 1% design wet bulb. Higher temperatures meant more ocean water was evaporated, which was apparently rising the local wet bulb and humidity which reduced the evaporative condenser capacity.

How do you design for a changing climate? That is something we are all trying to figure out. Following are a few suggestions to consider:

When looking at environmental data for a specific area, find the most current possible. Data that is even ten years old can be misleading.

Consider the future trend, which in many areas is hotter, and/or wetter, and/or colder. Climate patterns are more erratic as the total atmospheric movement of the planet changes due to increased temperatures, melting ice caps, and more moisture in the atmosphere. In designing for the future consider these temperatures and wet bulb trends and how they can impact the refrigeration loads and what equipment and materials to use while considering what can be economically justified.

Consider routing of piping and possibly using additional or different insulation, or different reflective surface coverings on piping.

Stay active in industry organizations such as IIAR and RETA where you can learn, access current information, current developments, recent design improvements, and many other areas and issues that can help make much more informed decisions when constructing and operating systems.

Use care when referring to older design guidelines, books, and articles. Many of these may be interesting from a historical perspective but were not written for a world experiencing climate change.

Climate change will affect how we design, construct and operate refrigeration systems.

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