Unique Methods for Analyzing Failures and Catastrophic Events by Anthony Sofronas

Author:Anthony Sofronas [Sofronas, Anthony]
Language: eng
Format: epub, pdf
ISBN: 9781119748274
Published: 2022-06-01T00:00:00+00:00

Figure 4.13.1 Gel ice pack cooler.

This design analyzes the possibility of a very small, low-cost ice cooler that is light and easily carried like a small fan.

A small gel ice pack, available in stores and used in picnic coolers, is frozen in the refrigerator freezer. A small personal cooling system based on this will be analyzed. The gel pack is envisioned as fitting into a picnic-type cooler with a small 115- or 12-V fan blowing ambient air on both sides. The warm air would be blown over the gel ice pack surfaces and would cool the air as shown in Figure 4.13.1, without humidity.

The idea sounds simple enough but there are questions. How long will the gel pack cool before having to be replaced with another from the freezer? What is the temperature of the cooled air? How far from the discharge will it cool someone? Some calculations can help quantify this.

A block of ice left in a warm space melts as it changes from a solid to a liquid. As it does it absorbs heat energy. Removing heat is what cools the air.

The latent heat of fusion is the heat energy needed to change ice to water. It is the amount of energy available to cool something down. Once it's used up, no more cooling is possible. From thermodynamic property tables, the amount of energy absorbed is 144 BTU/lb of the 32 °F ice used.

(4.1)

where Wice is the weight of the ice in pounds.

The first question is how long will this amount of energy last?, meaning how long before the ice all turns to cold liquid water?

For the flow of air (V) over surface areas (Atotal), the amount of heat transferred from the gel pack surface (q) is:

(4.2)

where ΔT is the temperature difference between one gel pack's total surface area (Atotal) and the ambient air temperature. The gel pack surface averages 42 °F with an airflow over it.

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