Heat Transfer and Solar Energy — Flashcards

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The three modes of heat transfer are: 1. CONDUCTION: Heat transfer through a material medium where molecules vibrate in their fixed positions and pass energy to neighbours. Common in solids. 2. CONVEC…

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Formula: Q = KA(T_h - T_c)t / d Where: • Q = Heat transferred (Joules, J) • K = Coefficient of thermal conductivity (W m⁻¹ K⁻¹) • A = Area of cross-section (m²) • T_h = Higher temperature (K or °C) •…

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Definition: The coefficient of thermal conductivity K is defined as the amount of heat transferred in one second across a material of cross-sectional area 1 m² and thickness 1 m, when opposite faces a…

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Given: • A = 2 m² • d = 0.02 m • K = 50 W m⁻¹ K⁻¹ • T_h = 100°C, T_c = 20°C → (T_h - T_c) = 80°C • t = 5 min = 5 × 60 = 300 s Formula: Q = KA(T_h - T_c)t / d Solution: Q = (50 × 2 × 80 × 300) / 0.02…

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Given: • Side = 30 cm = 0.30 m → Area of one face = 0.30 × 0.30 = 0.09 m² = 900 × 10⁻⁴ m² • d = 5 cm = 0.05 m • K = 0.01 J s⁻¹ m⁻¹ °C⁻¹ • T_h - T_c = 45 - 0 = 45°C • t = 6 h = 6 × 60 × 60 = 21600 s • …

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Wool traps air between its fibres. Air has a very low thermal conductivity (K = 0.025 W m⁻¹ K⁻¹), making it an excellent insulator. Mechanism: 1. Warm air gets trapped between wool fibres. 2. Low K o…

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Mechanism of Convection: 1. A fluid (liquid or gas) near a heat source gets heated. 2. It expands → its density decreases. 3. Due to reduced density, buoyant force pushes it upward. 4. Cooler, denser …

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Definition: Radiation is the continuous emission of energy from the surface of a body in the form of electromagnetic waves, without requiring any medium. Key Properties: 1. Speed: Travels at speed of…