Heat Exposure: A Game-Changing Approach to Ice Calculations

Heat Exposure: A Game-Changing Approach to Ice Calculations

The average perishable shipper looks at two metrics to determine how much ice to put in each box: 1) temp at destination 2) days in transit.  From there, they reference their table to determine how much ice to put in each box.

We’ve spoken in our previous posts about the deficiencies in this strategy; mainly, it doesn’t incorporate day-night cycle as well as the temperature along the way to the destination. That said, the ranges are arbitrary and have overlaps that spur inefficiencies.  

Introducing Heat Exposure as a Superior Metric

At Keep It Cool, we combine time and temperature into a single metric that we call Heat Exposure.  Heat Exposure is the average ambient temperature on the delivery journey multiplied by the duration of the trip.  

As exemplified by the green arrow in the above chart, a 1day shipment…say from Los Angeles to Las Vegas in the Summer would be a 25 hour journey with an average ambient temperature of 100F; therefore, 2500 Heat Exposure.  Similarly, a 50 hour journey from Boston to Chicago in the Fall would have an average ambient of 50F,resulting in a Heat Exposure of 2500.  

Heat Exposure in Action

Now let’s translate the above table into Heat Exposure to illuminate the suboptimal overlapping results:

The first row shows a destination high of 50F * 24hr delivery journey = 1200 Heat Exposure score. Similarly, a 50F destination high temp * a 48 hour transit = 2400 HeatExposure score.  

Uncovering Overlaps and Inefficiencies in Traditional Methods

As we fill out the columns with that formula, you see the folly of this strategy.  Specifically, there are one day trips that have lower Heat Exposure than 2 Day trips; however, the old matrix is recommending more ice. Take an 80F average ambient temperature trip in the third row (80F is the avg temp of the ISTA 7E profile) that has a Heat Exposure score of 1920 for a one day journey and compare that to the two day journey 50F and a Heat Exposure of 2400.  Do you see the inconsistency? The conventional thinking would employ less ice at higher Heat Exposure: 8lbs @2400 vs 12lbs @ 1920.  The energy that the different boxes will encounter on their delivery journeys is mismatched with the requisite ice.  

Consequently, these physics deniers over-ice a majority of 1 Day trips.  Furthermore, if we factored in the day night cycle on the 2 day trip, the heat exposure score would decrease; thus reducing the amount of ice required on 2 days as well.  

Transitioning to Heat Exposure: A Real World Example of Improved Ice Dosing

Here’s a visual of how the conventional thinking plays out in the real world with one of our customers prior to employing the KIC dashboard.

As you can see, they are dosing their medium box with differing coolant amounts given the same Heat Exposure.  This occurs when you make arbitrary cutoff points e.g. 65F, 80F, 95F on your coolant logic table instead of using a true metric of energy like Heat Exposure.  Zoom in on the 2000 level in the above chart.  Why would the same size box with the same product that is facing the same Heat Exposure require 10lbs of dry ice 21% of the time and 15lbs of dry ice 79% of the time?  Same answer: conventional coolant logic is flawed because of the arbitrary delineations between 1 day and 2 day across varying temperature ranges.

The Importance of Heat Exposure at Failure

Another complication from the conventional thinking revolves around the max Heat Exposure that a box can endure in its delivery journey.  All shippers send a number of boxes to a certain death each week before they even leave the dock.  These boxes are doomed because they haven’t been rated for a max heat exposure score. For each box size, we want to know the Heat Exposure at Failure with the maximum amount of ice that can fit in that box. In our small box example above, we know that the max ice the box can fit with its payload is 20lbs so we would run several live lane tests with 20lbs on routes that had high predicted Heat Exposure numbers.  After observing the real-world data, we would see that at 20lbs the small box succumbed to the elements around 4800.  Consequently, all shipments that will be subjected to the energy equivalent of 4800 Heat Exposure or greater would have their carrier service level upgraded as noted below.

Upgrading these doomed shipments and thereby eliminating the associated credits is a big part of the value that the Keep It Cool platform provides.

3 Key Takeaways

1.     Heat Exposure is a singular metric that combines time in transit and average ambient temperature along the delivery route.  It is superior to using destination high temperatures as your guiding criteria because it incorporates the day night cycle as well as the weather in every longitudinal and latitudinal point that your shipment will experience.

2.     Conventional Coolant logic serves up differing ice amounts for boxes of the same size that experience the same heat exposure.

3.     Understanding your Heat Exposure at Failure (at what Heat Exposure does your box fail given max ice) will enable the shipper to upgrade those boxes that our doomed to fail before they leave your dock.


Book a demo

Want to keep it cool? Let’s talk.
Book 15-minutes with Patrick, our founder and CEO.