I posted this study several years ago on another site and was recently asked to post on CR.
How efficient are heat packs when used to ship insulated boxes to maintain a warm temperature during the cold winter months in Michigan? Which heat packs should be used? What is the temperature of the water when received?
These are questions that have been on my mind when I ship coral frags during the winter months, so I designed a study to see how heat packs impact the shipped water temperature and the effectiveness of the insulated box. To design the study, many variables had to be controlled to make the proper comparisons meaningful, i.e. apples to apples. I used the same size and density Styrofoam containers, a uniform volume of water at a specific temperature and stored them in a controlled cold room at 4C +/- 1C (40F +/- 1F) degree. NIST calibrated temperature data loggers were sealed in plastic bags to keep them dry, then placed into the sealed water bag and recorded the water temperatures every 5 minutes for 48 hours.
Thank You
A special acknowledgement goes to Debbie Berlin (www.diyreef.com)/Todd Cherry (Cherry Corals) and Reefone for donating some different heat packs for testing and also for Jimsflies for helping me upload some of the data.
The Heat Pack Study follows below and in subsequent posts, however, I was having difficulty with the pdf files, so I have to convert the Excel charts to jpg format:
TEST CONTROLS:
First, every test must have some controls designed into the study for confidence in the results. Precision, accuracy, and blank samples are often used. For the purpose of precision, I started the study testing heat packs in triplicate to see if they were uniform in heating the water. After several tests on the Little Hotties, I concluded that testing in triplicate was no longer necessary as they were reproducible (precision). Accuracy is a little more difficult to show in this type of study, so the NIST calibration will have to suffice. In order to compare the results in a meaningful fashion, I prepared two blank controls, , blank meaning no heat packs. The first blank control was 27C bagged water with no Styrofoam box. The second blank was 27C bagged water packaged the same as the other tested boxes, but without any heat packs. These two blanks serve as control comparisons.
PACKAGING:
All packaging was uniform for every test (except the blank as described). A liter of 27C water was sealed with an activated temperature data logger in the bag, and then placed in the bottom of the Styrofoam cooler. A 2-ply newspaper was folded 4x and placed on the water bag as a barrier between the water and the heat packs. The heat pack(s) were taped to the inside of the lid and activated prior to use. Once assembled, a strip of tape was placed over the lid and sides of the box to make it secure, then placed in a temperature controlled environment. Shortly after 48 hours, the package was disassembled and the data logger downloaded to provide the readings and charts.
Last edited by BeakerBob; 03-09-2011 at 07:18 PM.
BeakerBob - Past MMMC Club President, current Board Member
STORAGE TEMPERATURE:
• Ambient temperature maintained at 4C
STYROFOAM CONTAINER:
• Thermalok TL-645F with lid
o Outside Dimension: 9-1/2 x 7-7/8 x 8-1/16,
o Inside Dimension: 6-1/4 x 4-5/8 x 5,
o Volume: 144.53 cubic inches, 2.4 liters, 0.634 gallons, or 81.15 ounces
o Wall thickness: 1.5”
WATER CONDITIONS:
• Volume: 1 liter, 0.26 gallons, or 33.8 ounces
• Temperature 27C (80.6F)
• Double bagged, no air bubble
TEMPERATURE DATA LOGGER:
• Recording interval: Set to record temperature at 5 minute intervals
• Duration: 48 hours
• Placement: Heat-sealed in plastic bag, double bagged and secured inside 1 liter water bag.
HEAT PACKS:
1. Little Hotties 18 hour Hand & Body Warmer, states 37C (135F) average temperature
2. DIYREEF.com, 20 hour Heat Pack, no other information available.
3. Grabber Mycoal 24+ hour Ultra Warmer, states 51C (124F) average temperature, 65C (149F) maximum temperature.
4. American Pioneer International, 30+ hour UniHeat, states 38C (100F) average temperature, 49C (120F) temperature
• Heat packs activated and warm prior to insertion into water bag
• Heat packs taped to lid along edges to maintain clear air holes
ASSUMPTIONS:
1) There is an adequate oxygen supply for the heat packs in the container.
2) Shipped packages are stored at an average of 40F during the cold winter months.
3) All packaging is prepared in a similar manner.
REAL LIFE VARIABLES:
1. The actual storage temperature (ambient temperature) is dependent on shipping environment.
2. Packaging varies in box size, density, and thickness which impacts heating efficiency.
3. Water volume is extremely variable and has significant impact on temperature.
BeakerBob - Past MMMC Club President, current Board Member
Temperature increase: The DIYREEF 20 hour and the UltraWarmer 24+ hour single and double heat packs actually raised the water temperature for a period of 3 to 5 hours to highs between 87F and 89F before decreasing.
At the 18 hour mark, typical of shipping out at 5PM one day and receiving at 11AM the next day, the water temperatures ranged from 61F to 65F.
At the 24 hour mark, the temperature ranged from 56F to 60F.
Lets open this to discussion for questions, comments, suggestions and what else might be explored in the future for this study. Don't forget to rate this thread to show if this type of information helps the reefing community or not. Rating can be done by clicking on the upper right portion of the first thread.
BeakerBob - Past MMMC Club President, current Board Member
Thank you so much for putting in the time and effort for this study! This is very interesting!
I would love to see a test done on the same heat packs to see what sort of difference poking a hole in the styro directly above the heat pack does.
I would also love to see hot hands brand tested as well if you do happen to do any in the future. The main heat packs I have seen used are: uniheat and hot hands. Hot hands seem to be available at all of the big box stores, so it would be interesting to see how they compare to the rest.
Last edited by rosebud161616; 03-09-2011 at 08:08 PM.
Heat Pack Study-Revisited
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