I watched Q119 this morning in Neenah Wisconsin and it was -13 degrees out. One of the trailers was a reefer that was running. What I was wondering is this: if a trailer or a reefer boxcar is hauling perishables like lettuce and it can’t freeze, how do the railroads (or trucking industry) keep items that are not supposed to freeze from freezing?
Paul
Could it have been a heater unit?
The package refrigeration unit heats the inside of the car as well as cools it, depending on what the thermostat asks it to do.
A refrigeration unit is a heat pump. It works in both directions, extracting heat from the inside of the trailer or reefer and pumping it to the atmosphere when it needs to cool, and extracting heat from the atmosphere and pumping it into the trailer or reefer when it needs to heat. Most heat pumps meant to function in the out-of-doors have electric heat coils to improve the heat pump’s efficiency.
A home refrigerator is also a heat pump, and it also heats during the “frost-free” portion. Every night it heats the inside of the freezer compartment to melt the frost, then rechills it. Most frozen food has enough mass to not appreciably melt during the heating cycle except for things like popsicles, which get kind of funky after a few weeks of being partially thawed every night.
RWM
Reefers work both ways in trucking.
I dont see any different for railroads.
I was lead trainer and later lead driver of a husband/wife reefer team. When it is winter time within certain temperatures, the unit just sits in a passive mode waiting for the temperature values to heat up or cool out of range before operating. GENERALLY but not always, it is set to cooling.
Having said that, truck reefer units hold up to 100 gallons under the trailer fuel for several days. They are capable of MAINTAINING the product temperature PROVIDED that the product is AT that temperature BEFORE loading. Usually truck reefers lack the BTU capacity to pull heat OUT of product and chill it down.
If you stick paint into a pre-warmed trailer at the dock at 60 degrees and close the doors. Setting the reefer to maintain 60 degrees inside that trailer will cause the unit to work in one direction… cooling to 60 in a hot summer day or WARMING to 60 in a freezing winter blast.
Hopefully that paint will see a room that is already at 60 degrees and it should not “Feel” any change in temperature through the entire trip no matter how hot or cold it gets outside.
There is something special about reefers we had and those on the railroads. They are constantly monitored for position GPS and Temperature values and other vital signs. If that reefer should QUIT… Carrier or Thermocool or whoever is the supplier of that particular unit will dispatch a mobile repair unit directly to the trailer or railcar location and have that unit repaired within hours.
The last time the reefer failed on me was in Grand Junction Colorado with a load of Mexican produce bound for Denver downtown. The steady hum of the unit (Which I dont even notice anymore) suddenly started to literally choke and gasp and quit. By the time the unit died, I had fell out of the bunk, punched off the brakes and swinging out onto I-70 running for Storm King, Vail etc right away. A load is at risk and the outside temperature was 50 degr
I have noticed Carrier and Thurmo King reefer units mounted on the end of the new reefer rail cars the last few years. It is the same units used on semi trailers. They must have 250 to 300 gallon diesel tanks mounted below them.
In Grand Rapids, MI. one night with a load that had to be zero or colder and the reefer came on. Checked the temps and it was -10 outside. So I got out and turned the unit off. You don’t make money heating a load up that doesn’t need to be.
Sir, if you are responsible directly for that cargo as a driver assigned to that load and know that the temperature can be allowed to drop below minimums to that of -10 or whatever without freezing or destroying what is inside that trailer then go ahead.
The cost of fuel keeping the load at whatever setpoint it may be at is aLOT cheaper than a lost load. A few dollars per hour and a few days fuel is no object whatso ever against load values approaching 2 million dollars or more.
If you are not involved with that unit at all and turned it off… you may have cost the load.
Sometimes the unit might be maintaining zero in -10 outside… not a problem.
What you dont want is a dead unit that is unable to start by itself or boot up. Those reefers RUN 24/7.
The only time those units are deliberately OFF is when the trailer is empty after unloading. And even then they are activated during pretrips and postrips to ensure that it is ready to go into pre-cooling for loading.
-10 degrees will be enough to thicken the unit, kill the battery cranking ability and generally create problems inside the engine compartment and when it is time for it to crank again… it wont.
In trucking desiels run at anything below zero. To have a dead engine in -10 is probably your life that will be paid.
You never EVER and I mean EVER screw with a reefer unit that is running. There is a reason why that unit is on. I used to haul stuff that if it got above -15 would EXPLODE and take out a 400 yard radius and that stuff was for the goverment. There are some loads worse than that VX nerve gas you never want that crap above 0 ot it will like to become an aroesol and then look out. When you see a reefer running constant at -zero temps there is one hell of a reason why. I pulled loads that were worth more than what they pay whole NFL teams in wages for a year and they were below zero temps.
The refrigeration unit exchanges heat and cold. If it is advanced enough it can maintain a temperature between 40 degrees and 32 degrees. Some perishables will be ruined if they are completely frozen and thawed.
Andrew
When I was young, my dad worked for PFE in the winter starting charcoal stoves to keep potatoes from freezing in reefers. The stoves were fastened in the ice bunkers. He had to be careful as charcoal puts out a lot of carbon monoxide.
dd
Bananas have to be maintianed above 56 F. A lower temperature for a length of time can cause the peel to spot. It won’t necessarily hurt the “Eatin’ Part”, but it will make this giant herb impossible to sell on a grocery shelf. Nobody will buy spotted bananas.
Bringing containers of bananas into Chicago from Gulfport, MS this time of year was always about keeping the temperature in the container above 56.
You want to keep fresh meat between 33 and 36. Salmonella (SP?) starts to multiply above 36 and if it gets frozen it’s no longer fresh meat.
There are charts with very precise temperature settings in the industry.
Pretty much everything shipped with either a cold set point or a heat setpoint and it is called temperature controlled.
One degree over and out of tolerance can either damage, destroy the product or as another poster said, break things and hurt/kill people.
The days of cranking that dial down to -40 and hearing the roar of the unit in highside cooling are over. Today is a world of computerization with alot of monitoring and reliablity.
The quickest way to wake me up in that truck is to have the unit quit completely. I slept through tornadoes, hurricanes, gunfire and other problems soundly but that silence… bounce out looking for trouble.
An interesting side effect of years in this work is when I am inside a tall building that has a steel beam core with a powerful environmental systems on the roof viberating and shaking the building along with that low hum… zzzzzzzzzz…
Those reefer units make too much noise and cause others to loose sleep. They should be turned off at night so others can get the rest they need. If you have things in that reefer that might blow up if they got warm , you should not keep your eyes off that load .
Expresslane alot of that stuff that does go boom if it gets to warm is also shipped in Dry Ice the Reefer unit is back up. People complain all the time about the noise reefers make YET EVERYONE LIKES TO EAT WITHOUT REEFERS WE AS A NTION WOULD STARVE SO BASICALLY EXPRESSLANE what I am saying is get used to it and deal with the noise I did all the time and never had a problem.
Reefers have actually gotten QUIETER over the last 20 years or so since I started playing with them. They purr these days instead of howling.
Never mind that noise, that is the sound of your groceries riding safe and fresh to your table.
Now, I do make an effort to sleep upwind away from the core mass of sleeping tractor trailers in the lot usually with the unit faced away from the pack so the trailer blocks the sound. It isnt always possible.
Some trailers carry TWO units to run TWO different temperatures with a bulkhead between.
Once in a while we even did LCL with the dry goods wrapped in the nose, bulkhead deployed then the food stuffs behind that. But there are certain products that never ever get shipped in a trailer used for foods for human use.
Maybe one day someone will invent a noiseless method to transfer calories and control the environment without using engines. I was looking at the new Sine drive on one of the recent HO scale offerings and wondered if made large enough and fed with sufficient power could such a device turn the compressor to keep a reefer cold?
Who knows?
I remember the first time I pulled a Whisper series by Thermo King I thought the dang thing was not running at all and kept checking it. Compared to the old SB3’s he has nothing to complain about at all.
Well, this is just a thought … but
If they’d take an insulated boxcar and put compartments at each end, then put ice in each compartment, and then hook up some kind of belt driven fan to the axle to move the air over the ice it just might do the trick. Certainly, it wouldn’t make much noise.
Been there, done that with the reefers before WW2.
The problem is this: Cooling.
You take lettuce from a hot california valley picked by the migrants and sent to the packer. The lettuce needs to be brought down to a required temperature so that it wont spoil.
It takes a HUGE amount of energy to bring that lettuce down. But once there, as long as you dont allow the transfer of heat the lettuce theoratically can stay like that forever.
The way I see it is this way, food spoils over time because there is life in that food. Corruption and death is the natural way to return that food to nature if it is not harvested otherwise after thousands of years of farming… we would be “Up to here” in crops that no one would want to eat.
Those reefers buy time to cross the great distance equal to crossing the atlantic in some cases to people far away who have no chance of growing lettuce themselves. They would have to build large towers that do nothing but farm crops using solar and a environment.
Think of it. A city full of towers that grow crops on 100 floors in temperatures, ground conditions and good protection against pests, dirty things and other problems. With enough of these towers farms would be obselete and trucking unnecessary.
Nah. It’s FUN to drive into Hunt’s Point past the blight and the rot to deliver good things to eat.
The problem with farms is water. Take the great land of Nebraska. There