Thermal Energy and Fuel Values

This page introduces important concepts related to the energy content of fuels and thermal energy calculations. It covers definitions of key terms and provides a practical example of heat transfer calculations.

Energy Content of Fuels

The energy content of fuels is defined in terms of heat of combustion or calorific value. These measures represent the amount of heat produced by burning a unit mass or volume of fuel.

Definition: Heat of combustion is the total amount of energy released when a unit mass or volume of a substance is completely burned.

Definition: Calorific value is the amount of heat released during complete combustion of a unit mass or volume of a substance, excluding the heat that could be obtained from condensing water vapor in the exhaust gases.

Nutritional Energy Values

The page also touches on concepts related to food energy:

Vocabulary: Digestibility is the ability of an organism to digest a given product, expressed as a percentage.

Definition: The energy value of food is the amount of energy in a given product that the body can absorb during digestion.

Thermal Energy Balance Calculations

The document includes a detailed example problem demonstrating how to calculate the heat required to change the state of water from ice to steam.

Example: Calculate the heat required to convert 500g of ice at -30°C to steam at 100°C.

The solution involves breaking down the process into several steps:

1. Heating ice from -30°C to 0°C
2. Melting ice at 0°C
3. Heating water from 0°C to 100°C
4. Vaporizing water at 100°C

Highlight: The problem solution uses the formula Q = mcΔT for heating phases and Q = mL for phase changes, where m is mass, c is specific heat capacity, ΔT is temperature change, and L is latent heat.

Key values provided include:

• Specific heat capacity of water: 4190 J/(kg·K)
• Specific heat capacity of ice: 2100 J/(kg·K)
• Latent heat of fusion for ice: 335,000 J/kg
• Latent heat of vaporization for water: 226,000 J/kg

The total heat required is calculated as the sum of heat for each step, resulting in 1,538,500 J.

Vocabulary: Bilans cieplny wzór (thermal balance formula) is demonstrated in this problem as the sum of heat required for each phase of the process.

The page also includes a second problem involving heat transfer between a steel ball and naphtha, illustrating the concept of thermal equilibrium.

Highlight: This example demonstrates practical application of bilans cieplny fizyka (thermal balance in physics) concepts in solving real-world problems.