Heat Transfer Fundamentals of Physics in Architecture I PDF

Dimensional Analysis Heat Transfer Fundamentals of Physics in Architecture I Degree in Architecture EPS Oct, 2...

Dimensional Analysis Heat Transfer Fundamentals of Physics in Architecture I Degree in Architecture EPS Oct, 2024 Degree in Architecture (EPS) Dimensional Analysis Oct, 2024 1 / 21 Dimensional Analysis Table of contents Types of Mechanisms. 1 FUNDAMENTALS. Measurement of quantities and Quantities and Units. units. Types of Heat. 2 CASES AND EXAMPLES. Degree in Architecture (EPS) Dimensional Analysis Oct, 2024 2 / 21 Dimensional Analysis FUNDAMENTALS. Table of contents Types of Mechanisms. 1 FUNDAMENTALS. Measurement of quantities and Quantities and Units. units. Types of Heat. 2 CASES AND EXAMPLES. Degree in Architecture (EPS) Dimensional Analysis Oct, 2024 3 / 21 Dimensional Analysis FUNDAMENTALS. Fundamentals. Quantities and Units. Types of heat. Types of mechanisms. Measurement of quantities and units. Degree in Architecture (EPS) Dimensional Analysis Oct, 2024 4 / 21 Dimensional Analysis FUNDAMENTALS. Quantities and Units. Derived Physical Quantities. The physical fundamentals in building systems are characterized by the seven base physical quantities mentioned above and the following derived physical quantities: Specific heat (Cp ). Latent heat (λ). Heat transfer rate (q). Heat flux (q/A). Thermal conductivity (k). Film coefficient (h). Thermal resistance (R). Overall heat transfer coefficient (U). Thermal gradient (dT/dr). Degree in Architecture (EPS) Dimensional Analysis Oct, 2024 5 / 21 Dimensional Analysis FUNDAMENTALS. Quantities and Units. Derived Physical Quantities. Quantity Dimensions S.I. Unit Specific heat (Cp ) L2 T2 θ−1 J/kgK Latent heat (λ) L2 T2 J/kg Heat transfer rate (q) ML2 T3 W Heat flux (q/A) MT3 W/m2 Thermal conductivity (k) MLT−3 θ−1 W/mK Film coefficient (h)) MT−3 θ−1 W/m2 K Thermal resistance (R) M−1 T3 θ m2 K/W Overall heat transfer coefficient (U) MT−3 θ−1 W/m2 K Thermal gradient (dT/dr) L−1 θ K/m Degree in Architecture (EPS) Dimensional Analysis Oct, 2024 6 / 21 Dimensional Analysis FUNDAMENTALS. Types of Heat. Types of Heat. There are two types of heat that can be transferred. Sensitive heat (Qs ). Latent heat (Qλ ). There are two important parameters related to heat transfer through building construction elements. Overall thermal resistance (R − value). Overall transmission coefficient (U − value). Degree in Architecture (EPS) Dimensional Analysis Oct, 2024 7 / 21 Dimensional Analysis FUNDAMENTALS. Types of Heat. Sensible heat. Sensible heat is the exchange of heat that results in an increase in temperature. Qs = m cp ∆T Where: Qs is the sensible heat transferred. m is the mass. cp is the specific heat. ∆T is the temperature increment. Degree in Architecture (EPS) Dimensional Analysis Oct, 2024 8 / 21 Dimensional Analysis FUNDAMENTALS. Types of Heat. Latent heat. Latent heat is a type of heat that is exchanged without an increase in temperature. This kind of heat causes phase transitions. Qλ = m λ Where: Qλ is the latent heat transferred. m is the mass. λ is the latent heat of the material. Degree in Architecture (EPS) Dimensional Analysis Oct, 2024 9 / 21 Dimensional Analysis FUNDAMENTALS. Types of Heat. Example 1. Latent heat. How much heat is needed to transform 0.5 kg of water at 100◦ C to steam at 100◦ C? Please note that the vaporization latent heat of water is λ = 2,3 × 106 J/kg. We have to apply the latent heat formula: Qλ = m λ = (0,5 kg) × (2,3 × 106 J/kg) = 1,15 × 106 J Degree in Architecture (EPS) Dimensional Analysis Oct, 2024 10 / 21 Dimensional Analysis FUNDAMENTALS. Types of Heat. Example 2. Sensible heat. How much heat is needed to raise the temperature of 2 kg copper form 20◦ to 70◦ ? Please note that the specific heat of copper is cp = 3,9 × 102 J/kg◦ C. Apply the formula of sensible heat: Qs = m cp ∆T = (2,0 kg) × (3,9 × 102 J/kg◦ C) × (50◦ C) = 3,90 × 104 J Degree in Architecture (EPS) Dimensional Analysis Oct, 2024 11 / 21 Dimensional Analysis FUNDAMENTALS. Types of Heat. Overall thermal resistance. The overall thermal resistance (R-value) is the sum of the conductive and convective resistances in a multilayer plane wall. q Tw − Tc = A R Where: Aq is the heat flux. R is overall thermal resistance (R-value). Tw is the warmest temperature. Tc is the coolest temperature. Degree in Architecture (EPS) Dimensional Analysis Oct, 2024 12 / 21 Dimensional Analysis FUNDAMENTALS. Types of Heat. Overall transmission (heat transfer) coefficient. The overall transmission coefficient is (U-value) the reciprocal of the overall thermal resistance (R-value). 1 U= R q = U(Tw − Tc ) A Where: Aq is the heat flux. U is overall heat transfer coefficient (U-value). Tw is the warmest temperature. Tc is the coolest temperature. Degree in Architecture (EPS) Dimensional Analysis Oct, 2024 13 / 21 Dimensional Analysis FUNDAMENTALS. Types of Mechanisms. Types of Mechanisms. Three types of mechanisms occur simultaneously during heat transfer. Conduction. Is the direct flow of heat through a material resulting from physical contact (via direct contact). Convection. Is the heat transfer mechanism between a surface and an adjacent fluid (liquid or gas)or by the flow of fluid form one place to another induced by temperature (via fluid). Radiation. Is a mechanism in which there is no medium required for the heat transfer. It consists in the transfer of thermal energy by electromagnetic waves (via electromagnetic radiation). Degree in Architecture (EPS) Dimensional Analysis Oct, 2024 14 / 21 Dimensional Analysis FUNDAMENTALS. Types of Mechanisms. Conduction. q Tw − Tc = A Rk Where: Aq : Heat flux. Rk : Conductive thermal resistance. Tw : Warmest temperature. Tc : Coolest temperature. Degree in Architecture (EPS) Dimensional Analysis Oct, 2024 15 / 21 Dimensional Analysis FUNDAMENTALS. Types of Mechanisms. Convection. q Tw − Tc = A Rc Where: Aq : Heat flux. Rc : Convective thermal resistance. Tw : Warmest temperature. Tc : Coolest temperature. Degree in Architecture (EPS) Dimensional Analysis Oct, 2024 16 / 21 Dimensional Analysis FUNDAMENTALS. Types of Mechanisms. Radiation. q = σ ϵ (T4s − T4sur ) A Where: Aq : Heat flux. ϵ: The emissivity of the material. σ: Stefan-Boltzman´s constant. σ = 5, 67 10−8 W m−2 K−4. Ts : The temperature at the surface of the object. Tsur : The temperature at the surroundings around the object. Degree in Architecture (EPS) Dimensional Analysis Oct, 2024 17 / 21 Dimensional Analysis FUNDAMENTALS. Measurement of quantities and units. Measurement of quantities and units. The quantities that can be measured are: Temperature T. Relative humidity H. Thermal gradient dt/dr. Relative humidity is a dimensionless quantity calculated by dividing the mass of water vapor present in the air by the total mass of air. Each of these quantities can be measured using the equipment described below. Degree in Architecture (EPS) Dimensional Analysis Oct, 2024 18 / 21 Dimensional Analysis FUNDAMENTALS. Measurement of quantities and units. Measurement of quantities and units. Thermometer. A thermometer is a device that mesures a temperature (T) or a thermal gradient (dt/dr). Pyrometer. A pyrometer is an instrument used to measure the temperature (T) of a substance without needing to make direct contact with it. This device measures the thermal radiation emitted by the object, allowing for the determination of its temperature. Thermohygrograph. A thermohygrograph is an instrument used to measure and record both the temperature (T) and the relative humidity (H) of the air. Thermographic camera. A thermographic camera is a device that measures infrared radiation emitted by objects and creates a thermal image that shows the thermal gradient (dt/dr). Degree in Architecture (EPS) Dimensional Analysis Oct, 2024 19 / 21 Dimensional Analysis CASES AND EXAMPLES. Table of contents Types of Mechanisms. 1 FUNDAMENTALS. Measurement of quantities and Quantities and Units. units. Types of Heat. 2 CASES AND EXAMPLES. Degree in Architecture (EPS) Dimensional Analysis Oct, 2024 20 / 21 Dimensional Analysis CASES AND EXAMPLES. Cases and Examples. Sensible heat and Latent Heat. Heat Transfer. Degree in Architecture (EPS) Dimensional Analysis Oct, 2024 21 / 21