Nusselt Theory for Filmwise Condensation क्या है? | Heat Transfer हिंदी Guide

Nusselt Theory heat transfer में filmwise condensation के analysis के लिए fundamental theory है। यह liquid film formation और heat transfer coefficient को calculate करने का method बताती है। इस ब्लॉग में हम Nusselt Theory, assumptions, derivation और applications हिंदी में समझेंगे।

1. Assumptions of Nusselt Theory

• Condensation occurs on a vertical plate or tube
• Condensate forms a thin liquid film over the surface
• Laminar flow in condensate film
• Negligible vapor shear effect
• Steady-state heat transfer
• Constant properties of liquid

2. Nusselt Theory Formula

For vertical plate of height L:

q = 0.943 * [(k³ * ρ² * g * h_fg * ΔT) / (μ * L)]^(1/4)

• q = heat transfer per unit width (W/m²)
• k = thermal conductivity of liquid
• ρ = density of liquid
• μ = dynamic viscosity
• g = acceleration due to gravity
• h_fg = latent heat of vaporization
• ΔT = temperature difference between vapor and surface
• L = vertical length of plate

3. Key Points

• Heat transfer rate depends on film thickness, fluid properties and temperature difference
• Laminar film assumption simplifies calculation
• Applicable for vertical surfaces and horizontal tubes with modifications

4. Practical Applications

• Condensers in power plants
• Evaporators and distillation columns
• Design of cooling surfaces in chemical and HVAC industries

निष्कर्ष

Nusselt Theory filmwise condensation के heat transfer analysis का मूल आधार है। यह liquid film की thickness, surface orientation और fluid properties के आधार पर heat transfer coefficient calculate करने में मदद करती है। Engineering applications में condensers, evaporators और heat exchangers के design में इसका व्यापक उपयोग होता है।