Chapter 4: Heat Capacity and Flow

• Chapter 4 focuses on heat and its flow in biological systems, including medical applications

Heat Capacity

• Heat Capacity describes amount of heat energy needed to raise a substance's temperature by one degree Celsius
• Is the amount of heat energy required to raise the temperature of a sample by 1 degree Celsius
• The amount of heat added to a substance equals temperature change multiplied by the heat capacity, with the unit being J/°C

Specific Heat Capacity

• Specific Heat Capacity is with the division of heat capacity by mass
• Specific heat capacity depends only on the type of material
• Specific heat capacity describes amount of heat energy needed to raise one kilogram of the substance's temperature by one degree Celsius
• Heat quantity can be calculated as Q = mcΔT, where Q is heat transferred, m is mass, c is specific heat capacity, and ΔT is the change in temperature
• Water has a high heat capacity of 4186 J/(kg·°C)

Thermal Measurements

• Temperature readings in Celsius (°C), Fahrenheit (°F), and Kelvin (K) are used in thermal measurements
• Celsius, Fahrenheit, and Kelvin are related by formulas; Tk = Tc + 273, T = (9/5)Tc + 32

Latent Heat

• Latent heat is the heat required to change its state without raising its temperature
• The heat needed for a phase change is Q = mL, where L is the latent heat of fusion/vaporization
• The latent heat of fusion for ice is 3.35 x 10^5 J/kg
• The latent heat of vaporization for water is 2.26 x 10^6 J/kg

Heat Exchange

• The body exchanges heat with its surroundings through metabolic processes
• Metabolic processes are the body's primary energy source
• Humans require about 2500 kcal daily
• The consumption of energy by the body is measured in "met" units, where one met equals an energy consumption of 50 kcal per square meter of body surface per hour

Basic Metabolic Rate

• Metabolic Rate is the rate of energy expenditure by humans, animals, and machines, usually measured in watts
• The basic metabolic rate (BMR) estimates the minimum amount of energy the body needs to function
• Depends on thyroid gland activity and body surface area and mass
• It increases with body temperature

Body as a Machine

• The body's efficiency as a machine is how well it can work
• The body converts biochemical energy into mechanical energy, which has a limited efficiency
• The mechanical energy can be measured using an ergometer, which measures power output, speed, time, and oxygen consumption

Methods of Heat Loss

• Heat loss from the body occurs through radiation, convection, evaporation, and conduction.
• The hypothalamus in the brain controls body temperature
• The body temperature must remain constant to stay healthy

Radiation

• Radiation happens when heat is lost or gained caused by electromagnetic waves
• Heat can be transferred through a vacuum
• Stefan's law describes heat transfer by radiation and is given by ΔQ/Δt = σεAT^4

Convection

• With convection heat moves whenever a fluid flows through the area
• It happens from a material's changing temperature and density
• The amount of moving heat will vary depending on how much fluid there is

Conduction

• The flow of heat through direct contact
• . Heat flows through a substance when there thermal difference
• The amount of electricity required for this process depends on the type of material
• The transfer depends on of size and form
• Heat Conduction varies depending on the material being used