Department of Architecture & Civil Engineering University of Fukui, JAPAN Presented by: Prof. Dr. T. Fukuhara Production Model of TSS Based on Condensation Theory CONF. IV ISES & XVII SPES November 1~5, 2010, Cusco, Peru Environmental H eat and H ydraulics Lab. T ubular S olar S till (TSS) ? Using Solar Energy Saline water Distilled water
CONTENTS 1. INTRODUCTION 2. PRODUCTION MECHANISM OF TSS 3. THEORY OF CONDENSATION 4. INDOOR EXPERIMENTS 5. FIELD EXPERIMENTS 6. CONCLUSIONS Environmental H eat and H ydraulics Lab.
<ul><li>Remote and arid areas </li></ul><ul><li>After natural disaster </li></ul><ul><li>(tsunami, tornado, etc.) </li></ul> Desalination - Solar distillation 1. INTRODUCTION Tubular Solar Still (TSS) (We developed) Easy fabrication, set-up & maintenance Shortage of drinking water Electricity Transportation RO In developing/ under developing countries MSF MED ED Fig. Women collecting drinking Water (Bangladesh) Fig. People collecting water from nearly dried-up well (Nigeria) Fig. Women transporting drinking water (Sudan) Fig. Unsafe water source due to tsunami Environmental H eat and H ydraulics Lab.
Water troubles in Bangladesh Red paint A hand pump well contaminated by arsenic 35 million people ( 1/4 of population ) danger of diseases due to arsenic
Diseases caused by arsenic Keratosis Gangren Cancer Melanosis
Safe area Iso-concentration of Chloride ion ( Cl - ) Drinking Water Standard: 200 mg/L (Critical value of Japanese standard)
50km Prediction of sea water intrusion due to rise in sea water table （ from IPCC ）
Pond water for drinking purpose Small volume and high turbidity at the end of dry season
P ond s and f ilter （ PSF ） Pumping up pond water to PSF with a hand pump Hand pump well Sand filter
Woman pumping up pond water to PSF with a hand pump A lot of women must wait for 2-3 hours to get water! Drawing water is the duty of women .
It takes 30 minutes to fill a vessel of 10L Some people come from 16km away. Small rate of water from PSF
Many people like her cannot stand waiting for good water. Take water directly from pond. People also use pond water for daily life . Reason: 240 PSFs for 240,000 people
Practical purpose <ul><li>Solar desalination facility for on-site usage </li></ul><ul><li>with low cost and easy maintenance </li></ul>Sea water Long transportation Non CO2 emission ・・・ Suitable for developing countries 長距離水輸送 Power plant Large scale desalination plant Small size On-site usage CO2 F.W. Near CO2
1. INTRODUCTION (Cont..) Objectives of this paper: 1. Propose a production model based on a condensation theory for a TSS. 2. To use a new overall heat transfer coefficient between the humid and ambient air in the proposed model. 3. Verification of the proposed model by comparing indoor and field experimental data. Environmental H eat and H ydraulics Lab.
2. PRODUCTION MECHANISM OF TSS Fig. Production Principle of TSS (Production) Environmental H eat and H ydraulics Lab.
Conventional production models for basin type still based on evaporation theory. - Evaporation Condensation Production Theory of condensation may give a better result than past evaporation theories. Conventional production models A time lag Present model 2. PRODUCTION MECHANISM OF TSS New & unique model No theory of condensation for solar stills RH ha T ha Inside TSS Outside TSS Environmental H eat and H ydraulics Lab.
3. THEORY OF CONDENSATION Fig. Condensate liquid film & gravity force at point P δ is gradually Increases in downward dir. small element Water Environmental H eat and H ydraulics Lab.
Fig. Representative element of liquid film flow Interface 3. THEORY OF CONDENSATION (Cont..) Atmosphere Liquid film Humid air Cover v Axial () dir. x Angular ( ) dir. Velocity profile Liquid film Humid air d Cover r r=R r=R- dx =1 d ds=Rd Environmental H eat and H ydraulics Lab.
Fig. Temperature profile Fig. Heat & mass transfer 3. THEORY OF CONDENSATION (Cont..) i Atmosphere Cover Liquid film Humid air Environmental H eat and H ydraulics Lab.
3. THEORY (Cont..) Energy equation: in a steady state Momentum equation: in a steady state Refer to the paper for assumptions and BC Environmental H eat and H ydraulics Lab.
3. THEORY (Cont..) Energy Eq. Fourier’s Law Integrate using BC h l Apparent heat flux Actual heat flux Using local HTC Area fraction Temp. correction coefficient Condensation coefficient Environmental H eat and H ydraulics Lab.
3. THEORY (Cont..) Momentum Eq. Mass flow/ L Integrate using BC Film thickness Local HTC Heat flow/ L Average HTC Environmental H eat and H ydraulics Lab.
3. THEORY (Cont..) Average HTC A new overall HTC m Mass flux Temp. difference fraction Condensation coefficient Indoor Expt. Indoor Expt. Atmosphere T a Environmental H eat and H ydraulics Lab. i
4. INDOOR EXPERIMENTS Fig. Schematic diagram of indoor experiment Experimental Conditions T a :15, 20,25,30 & 35 o C RH a : 35% R s :1200,800,500W/m 2 Expt. duration: 8 hrs. Water depth: 45mm (to measure evaporation) Evaporation Evaporation Distilled water (Production) Production Environmental H eat and H ydraulics Lab.
Fig. Relation between ( T ha -T ci ) and ( T ha -T a ) 4. INDOOR EXPERIMENTS - RESULTS Environmental H eat and H ydraulics Lab.
Fig. Relation between γ c and e a /e o e a =e o -e vha e vha =f ( T ha , RH ha ) e o = 101325Pa 4. INDOOR EXPERIMENTS - RESULTS RH ha << 100% Environmental H eat and H ydraulics Lab.
Fig. Diurnal variations of T and RH (Fukui, 2005) RH ha ≈ 50% during daytime RH ha 5. FIELD EXPERIMENTS - RESULTS Unsaturated T ha T a Environmental H eat and H ydraulics Lab.
Fig. Diurnal variations of observed p h and calculated m h Sep 29 Oct 6 5. FIELD EXPERIMENTS - RESULTS No time lag Environmental H eat and H ydraulics Lab.
6. CONCLUSIONS 1. A production model based on condensation theory for a TSS is developed. 2. The condensation coefficient, 3. The condensation theory using h o could provide a good agreement with laboratory experimental data. 4. The validity of the model is evaluated from the comparison with field experimental result. 5. The condensation theory can be used to precisely predict the production flux . Environmental H eat and H ydraulics Lab.