Cold Weather Basics. NWH District Ted Shreve

Size: px

Start display at page:

Download "Cold Weather Basics. NWH District Ted Shreve"

Abel Allen
5 years ago
Views:

1 Cold Weather Basics NWH District Ted Shreve

2 Cold Weather Basics Learning Objectives Heat Transfer Radiation Convection Conduction Evaporation Respiration Weather Wind Chill Water Chill Types of Cold Wet-Cold Dry-Cold Arctic-Cold Why does Flick s tongue stick to the cold metal flag pole?

Radiant Heat Loss Leading cause of heat loss The head and ears are very efficient in removing body heat. Heat loss from an unprotected, uncovered head can be enormous.

3 Radiant Heat Loss Leading cause of heat loss The head and ears are very efficient in removing body heat. Heat loss from an unprotected, uncovered head can be enormous. An unprotected head may release the following percentage of the body's total heat production 50% at 40 F (4 C) 75% at 5 F (-15 C). The world has a greater capacity to adsorb Heat than we have to generate it.

Heat Loss Convection Imagine we have a hole in the pot and constantly Have to refill it with cold water, while the leak puts out Our fire, Will it ever boil? This is when trapped body heat escapes.

4 Heat Loss Convection Imagine we have a hole in the pot and constantly Have to refill it with cold water, while the leak puts out Our fire, Will it ever boil? This is when trapped body heat escapes. Through radiation, the body continuously warms a thin layer of air next to the skin to a temperature nearly equal to that of the skin. When this warm-air layer is retained close to the body by clothing, you remain warm. Proper fit Properly closed If this warm layer of air is constantly being removed by the wind (convection), you will get cold.

5 Heat Loss Conduction Back to Flick s Tongue Direct contact with really cold stuff. Metal Gasoline/Solvents Rocks The Frozen Ground Can freeze the water in your skin cells instantly = Frostbite

Heat Loss Evaporation Cotton Kills He s not wearing any Neither should you! The evaporation of sweat from the skin accounts for a substantial loss of body heat.

6 Heat Loss Evaporation Cotton Kills He s not wearing any Neither should you! The evaporation of sweat from the skin accounts for a substantial loss of body heat. Wearing fabrics that "breathe and do not hold water is critical when winter camping. If water vapor cannot pass freely through your clothing, it condenses and you become wet and very cold. Moisture Management

7 Why Cotton Kills & Clean Dry Clothes Matter! The amount of energy required to Evaporate water 2500 Joules/gram No change in temperature Goes from liquid to a vapor Adsorbs energy from the air (cooling) Heat water Joules/gram Heat 1 gram of water 1 degree C Volume = 1 cubic centimeter Small Volume Heat air Joules/gram Heat 1 gram of dry air 1 degree C Volume approx. 1 cubic meter Large Volume Moisture is an Energy Hog when Winter Camping

8 Heat Loss Respiration Inhaling cool dry air and exhaling warm moist air accounts for a significant amount of heat loss. The lungs are designed to transfer Oxygen but they transfer heat as well. Exhaling into your clothing, sleeping bag, or tent will generate moisture.. Controlled ventilation or Moisture Management

9 Wind Chill Even the slightest breeze will draw body heat from you in cold weather. Heat moves to cold The air acts a heat sink with an infinite capacity compared to your body s ability to generate heat Frostbite starts to occur quickly on unprotected skin

Water Chill Keeping wet clothes warm or trying to dry them with body heat alone is virtually impossible due to the large amount of energy required.

10 Water Chill Keeping wet clothes warm or trying to dry them with body heat alone is virtually impossible due to the large amount of energy required. Moisture and dirt fill the air pockets of fabrics so they can now conduct or wick heat directly away from your body. One of the reasons wool still provides insulating value when damp is that it has a unique fiber structure that wicks moisture and traps it without affecting the air insulating pockets in the cloth. Wet wool can actually generate heat Through a chemical reaction that occurs Within the wool fiber!

11 Wet-Cold 50 F- 14 F Wide Temperature Swings Freeze Thaw Cycle Moisture Management Dry-Cold 14 F to minus 20 F Wind Frozen Ground Arctic-Cold Less than minus 20 F Wind Materials and Equipment issues Types of Cold

12 Wet-Cold Most common type of winter camping we will take part in as Scouts. Moisture Management is the key to successful events. Everything will get wet and muddy. Expect it. Plan for it. Set these expectations with parents and Scouts Trench foot!

13 Dry-Cold Wind and Cold Frozen Ground are the enemy when camping in this type of weather condition. Insulation and Wind Protection Wet-Cold can turn to Dry-Cold in less than a 24 hr period.

14 Arctic-Cold (Sustained Temperatures of -20 F) This type of expedition is beyond the scope of Boy Scout winter camping! Unless you have $pecialized equipment and training beyond what we are doing today.. Our advice is: Pack up and go home or don t leave in the 1 st place unless you have heated shelters to escape into. Hiromasa Andow Completes 5000 mile Bicycle Trip across Siberia May 2005

More heat energy means more of what type of energy? Does the mass change? So, what must change? What is the same in both containers?

More heat energy means more of what type of energy? Does the mass change? So, what must change? What is the same in both containers? Quest Chapter 21-23 # Problem Hint 1 When a container of gas is heated, what happens to the average speed of its molecules? 1. Additional information is needed. 2. increases 3. doesn t change 4. decreases