Feasibility Analysis of a Two Phase Solar Thermal Water Heater Solar Thermal Solutions (M15) Project Supervisor: Dr. Y. Muzychka April 3 rd, 2014 Marcus Davis Steve Youden Brain Hurley Kyle Snow

Agenda Introduction Supporting Theory System Overview Testing and Analysis Feasibility Analysis Results Sources of Error and Recommendations Budget Overview

Problem Statement It is unclear if the introduction of two-phase uniformly segmented plug flow to a flat plate solar collector is feasible

Objectives Introduce stable two-phase segmented flow to a solar thermal water heating system Evaluate effectiveness and economic feasibility of introducing this flow to a flat plate solar thermal collector as a retrofit design

Project Constraints Time (3.5 months) Financial ($450) Functionality ◦ Fluids constrained to water and air ◦ Freeze protection not considered Equipment (i.e. pump, compressor) Testing conditions (thermo lab)

BACKGROUND THEORY

Solar Collectors Solar Collector Cross Section & Top view (Duffie & Beckman, 2013) Special type of heat exchanger ◦ Differs from ‘normal’ heat exchangers that have fluid to fluid heat exchange ◦ Converts solar radiant energy to thermal energy

Two-Phase Flow Segmented fluid flow Results in increases circulation of liquid segments, increasing heat transfer

Two-phase flow heat transfer/pressure drop model Note: Air bubble lengths < 3 were difficult to create and maintain Optimization Model Liquid Length =10-20 Air Length = 3-6

SYSTEM DESCRIPTION

Collector Selection Two options for collectors: ◦ NovaSolaris heat collector ◦ Purchase solar thermal collector Decision made to move forward using the readily-available NovaSolaris heat collector Decision Table

System Description

SYSTEM PREPARATION FOR TESTING

Goal For Preparation 1. Create and observe stable, controllable two-phase segmented flow before introducing the phenomenon to heat collector 2. Integrate heat collector into system while preserving the segmented flow quality

Preliminary Flow Testing Initial observations showed resemblance of two-phase segmented flow ◦ The air plugs usually segregated ◦ Liquid segments carried significant amount of residual air bubbles Suspected that the configuration of the air injection manifold root of flow issue

Air Injection Manifold Modifications 1. Inject air through a smaller orifice ◦ Keeps bubble from segregating 2. Reduce residual air space in manifold ◦ Minimize air in liquid segments

Heat Collector Integration Found quality of two-phase flow significantly degraded within collector ◦ Attributed to copper tubing configuration Need to reduce from 6 to 3 passes to preserve integrity of experiment

Final Flow Quality

FEASIBILITY ANALYSIS METHODOLOGY

Feasibility Analysis Methodology Energy Gained = E collector - E pump Single-Phase System

Feasibility Analysis Methodology Energy Gained = E collector - E pump - E control - E compressor Two-Phase System

Feasibility Analysis Methodology Energy Gained (Single-Phase) Energy Gained (Two-Phase) Energy Gained = Energy Outputs – Energy Inputs < Prove:

TESTING AND RESULTS DOE Testing Phase Intermediate Testing Phase Feasibility Analysis Testing Phase

Design of Testing Program DOE (two-factorial experiment) used to develop testing program ◦ Checks significance of two-factor interaction ◦ Identifies significance/sensitivity of factors ◦ Validates/determines further experiment ◦ Feasibility Analysis based on optimized values DOE Testing Phase Intermediate Testing Phase Feasibility Analysis Testing Phase

Design of Testing Program Variables for experiment ◦ Length of Liquid Segment ( β ) ◦ Length of Gas Segment ( δ ) ◦ Mass Flow Rate ◦ Angle of Collector

Results of DOE Testing 12 tests performed Conclusions drawn: ◦ Significant model (F-value 5.69 > 4) ◦ No significant 2-Factor interaction ◦ Most significant Factors are:  Angle of Collector  Length of air bubbles Went Forward Using Best Observed Conditions

Intermediate Testing 3 additional tests performed Confirmed that test 4 condition will be used for feasibility analysis DOE Testing Phase Intermediate Testing Phase Feasibility Analysis Testing Phase

Optimization Model Comparison Experimental results show general trend of optimization model

Feasibility Analysis Testing Used best two-phase conditions from DOE and intermediate testing DOE Testing Phase Intermediate Testing Phase Feasibility Analysis Testing Phase

Two-Phase versus Single Phase Δ Q ≈ 100W

FEASIBILITY ANALYSIS RESULTS

Additional components required for retrofit Two-Phase Enhancement = 28% Extra Energy Gained = 0.28 x $ = $72.55 Extra Value Gained = $ $10 Maintenance = $62.55 Payback Period of Equipment = $220 / $62.55 ≅ 3.5 years Feasibility Results

SOURCES OF ERROR

Sources of Error Pump Size (Dultmeier Hypro Shertch 1.5 HP)

Sources of Error Flow rate measurements (human factors) Compressor Gauge Precision Data Collection System Accuracy (Calibration) Heat Loss Assumptions

Recommendations Smaller Pump – 4.2 L/min Flow-meter – 0.5 L/min-5L/min Run longer tests Higher precision regulator/gauges on compressor Complete feasibility analysis on a commercially available collector under Newfoundland conditions

PROJECT MANAGEMENT

Project Budget

QUESTIONS? Acknowledgements: Dr. Muzychka, Craig Mitchell, Tom Pike, Glen St. Croix, Don Taylor Summary: Two-Phase Energy Gain versus Single Phase = 28% Payback period = 3.5 years

System Description Divided into 3 different areas Heat Collector Subsystem Heat Collector, Pump, Reservoir, Intermediate Tubing Air Injection Subsystem Compressor, Air Injection Manifold, PIC controller Data Collection Subsystem Datalogger, Pressure and Temperature Transducers

Performance versus Predicted Experiments aligned with predicted values