Design of Heat Exchanger for Solar Still Application

Team Technik’s Presentation

Meet the Team

Joshua Praveen R

B.E. Mechanical 3^rd year

Sri Venketeswara College of Engineering

Ajith A

B.E. Mechanical 3^rd year

Sri Venketeswara College of Engineering

Ashwin Kumar V

B.E. Mechanical 3^rd year

Sri Venketeswara College of Engineering

Formulation of Design Concept

• Can be derived using heat transfer equations

• Either outside the Still or inside the Still

Based on Heat Required inside the Still

Solar Still

Radiation

Convection

Evaporation

• Heat produced due to Evaporation plays a vital role in producing fresh water vapours from the Still

• Heat produced due to Radiation from the Sun

• Heat liberated by Convection through the walls of the Still

Heat Calculations For Solar Still

Rate of Heat Transfer by Convection,

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Rate of Heat Transfer by Evaporation,

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Rate of Heat Transfer by Radiation,

Where,

Tw – Temperature of Water inside the Still

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Tg – Temperature of Still glass

Pw – Vapour Pressure of water

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Pg – Vapour Pressure of Glass

Iterative Results

Iteration Variable = Tw

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Desired End Result = Mw

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Constraint = Tg

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Observed Values = Qc, Qe, Qr & Qt

Where, Hourly Yield of Fresh water,

Hence, for the desired yield of fresh water to be achieved the Brackish water in the still mut be heated to the corresponding temperature such that the required rate of heat is transferred.

Based on Position of Heat Exchanger

Possible places for positioning the Heat Exchanger

Inside the Solar Still, placed within the Charcoal Bed

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Outside the Solar Still, for pre-heating the brackish water

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Advantages of placing the Heat Exchanger within the Still

Disadvantages of placing the Heat Exchanger outside the Still

Hence, the formulation of Heat Exchanger Design and Calculation is made based on its position inside the still with the charcoal bed

Concept Design

Concept Design - 3D Model�

Solar Still

ETC

Heat Exchanger

Solar Still Design

Double layer glass

Black coated GI sheets

Wooden Insulation

Gutter

Evacuated Tube Collector Design

Copper tube filled with small amount of Ethylene glycol

Evacuated Glass Tube

Lobe

Steel Duct

Heat Exchanger Design

Connector

Heat Exchanger Calculations

Rate of Heat transfer by conduction and convection, Q = (Ti – To)/R

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Where,

Resistance to heat transfer, R = R1+R2

(R1 = 1/(2*π*L*r1*hi)) (R2 = ln(r2/r1)/(2* π*L* k1))

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Since, Q = (Ti-To)/R = (T2-To)/R2

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Surface Temperature of Heat Exchanger (T2) is found

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r1

r2

hi, Ti

k1

To

T1

T2

R1

R2

Flow Analysis of Heat Exchanger

Inlet Velocity: 3 m/s

Maximum pressure acting: 260 Pa

Thermal Analysis of Heat Exchanger

Inlet water Temperature: 65° C

Coefficient of heat transfer by convection between water and copper: 395 W/m^2 K

Generative Design Usage

Advantages of our Heat Exchanger Design

• The heat exchanger designed will be adding on to the hourly yield of the solar still, as the heat produced due to evaporation will be more than the heat produced in a solar still without the heat exchanger.
• Placing the heat exchanger in-between the charcoal bed, will increase the thermal efficiency of the still
• Heat absorbed by the charcoal from the exchanger will be liberated and maintains a steady temperature inside the still
• The double layer glass will maintain an optimum temperature inside the still at non-peak sunlight hours
• The motor consumes the energy from the solar cells. Hence, the system is completely solar energy based

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Thank You