Post on 27-Apr-2020
Design and evaluation of open
volumetric air receiver for process
heat applicationsP. Sharma, R. Sarma, D. Patidar, G. Singh, D. Saini, N. Yadav
L. Chandra*, R. Shekhar, P. S. Ghoshdastidar
Centre for Solar Energy Technologies
Indian Institute of Technology Jodhpur, Rajasthan, India.
*Corresponding author: chandra@iitj.ac.inInt. Workshop on Design of Sub-systems for Concentrated Solar Power Technologies,
19-21 December 2013, Jodhpur.
Contents
1. Motivation
2. Objectives
3. Design Methodology
4. Volumetric Air Receiver Design and Analyses
5. SATS Facility
6. Conclusion
1. MotivationIndigenous adopted design of open volumetric air receiver(in view of local condition) for industrial process heatapplication.
Solar Convective Furnace
Avoid double conversion: Fuel Heat Electricity Process heat
Receiver
Retrofitted Furnace
1.1 Retrofitted FurnaceIn Design Stage for Aluminum Heat Treatment
Hot Air in Hot Air in
Aluminum Ingots
Hearth grid
Backup (existing) electric heaters
Furnace Hearth
Hot Air Ducts
2. Objectives
Design aspects of open volumetric air receiver
a. Flow instability;
b. Components, such as, mixer, air-recirculation system, porous receiver;
Evaluation of the designed receiver
3. Design Methodology
- Preliminary analysis “A” Design
- Detailed experiment Final Design
Need An experimental set-up: Designed and installed
3.1 Preliminary analysis
Special Consideration: Flow instability at high temperature
Analysis Capture flow instability
Need A validated tool
3.2 Validation: FLUENT is selectedSelected experiment: Fend et al. (2004)
Case PoA,
kW
MFR
(kg/s)
PoA/MFR
(kJ/kg)
Air outlet temp.
(K)
Efficiency (%)
1 2.88 0.0046 626 728 76
2 3.69 0.0046 803 850 75
3 4.41 0.0062 710 818 80
4 4.8 0.0065 743 866 83
5 5.35 0.0065 823 928 83
6 5.32 0.0066 810 936 85
7 4.33 0.0068 636 843 94
Fig. 1. 20 PPI SiC foam used for the experimental purpose by Fend et al., 2004 (Ø80X30mm)
3.2 Validation: Analyses
- CFD analyzed results within experimental error limit ± 5%.
- Larger deviation only in 1 out of 7 cases is observed.
- Best practice: Temperature dependent material properties should be carefully modeled
3.3 Flow instability
SiC~ 111-150 W/mKNo flow instability
Metal~ 15-30 W/mKFlow instability is expected
Condition in which the effect of thermal conductivity can be ignored: (refer to the article for derivation)
Order of magnitude analysis »
Circular (porosity ~50%) Square (porosity ~ 75%) Hexagonal (porosity ~ 55%)
RadiationRadiation
Radiation
Porous body (receiver) type Channels/inch2 Df,eff/L
SolAir 200 receiver (square channel) 90 1.401
Circular design (IIT Jodhpur) 104 0.713
Hexagonal design (IIT Jodhpur) 144 0.837
Square design (IIT Jodhpur) 154 0.974
4. Volumetric Air Receiver Design and Analyses
Target: 1. Effect of porosity; 2. Effect of geometry
4.1 Circular Design
Design consideration: Porous receiver assembly with foot piece; air re-circulation system; mixing plate; mixer etc.
4.2 Receiver assembly
Components of open air receiver and assembly
All the components are designed with the help of selectively validated FLUENT code
4.3 Mixer Design (an example)Mixer plate
Convergent
nozzleCases Inlet typeNo. of Inlet
(quarter)Arrangement R’ Dp (mm)
I Circular 2 Non staggered 1 14.4 Angle: 9.54°
Length:139.4mm
Outlet diameter:
50.8mm
II Circular 3 Non staggered 1.5 14.4
III Elliptical 3 staggered 1 and 1.5 9 and 5.56
IV Circular 3 staggered 1 and 1.5 14.4
• Design case IV is selected based on detailed analysis
Maximum inlet temperature difference: 50 °C/KMaximum outlet temperature difference: 11.5°C/K
2
4
6
8
Air re-circulation system
Why? – Non-uniform cooling of porous receiver Thermal Stress Failure
Solution: Ensure uniform cooling
Air-recirculation system
(injection)
Velocity (m/s) Contour: Injection plane Velocity Contour: outlet plane
Uniform velocity Uniform cooling Mitigation of thermal stress
Surface temperature on porous receiver with 6 inlet
Temperature contour (RANS CFD analyzed)Turbulence model: Reynolds stress
2nd Order approximation
Experiment and CFD analysis: Power = 0.45 kW
Non-uniform temperature leads to thermal stressAir-recirculation system needs special attention
Temperature measurement
locations
Flow Rate (gm/s)
6 8 10
Expt Model CFD Expt Model Expt Model
Input Recirculating air inlet 33.6 33.6 33.6 34.6 34.6 36.7 36.7
Primary air Outlet 102.7 102.7 87.6 87.6 82.7 82.7
Output
Recirculating air
outlet 51.6 43.0 49.6 46.9 41.1 46.7 42.4
Mixed (Primary air
inlet to receiver) 53.3 40.4 47.7 40.4 46.6 45.3
Flow rate = 6g/s(in C)
0.5970.345ReNu
5. 4kWth Solar Air Tower Simulator (SATS) Facility
Open volumetric air
receiver assembly (A)
Electrically heated
A Receiver assembly,
B Heat exchanger,
C Blower,
D Thermal energy storage,
E Direct storage line,
F Secondary line
Target air temperature: 450
5.1 Experiment: Conditions
Receiver: Electrically heated
- Receiver material: Brass;- Power input = 750kW - 1.5kW; - Equiv. suns on porous receiver ~ 210- 420;- Volumetric heating is ensured;
POA/MFR(kJ/kg)
Average receiver
Temp. (C)
Air Temp. (C) at the outlet of
porous receiver
Re-circulating air inlet temp.
(C)
Re-circulating air outlet temp. (C)
Efficiency (heat
removal/power input)
250 286 270 33 78 >90%
5.2 Experiment: Measured data for 1.25kW
Fig. : Receiver Temperature: Radial and Azimuthal (solid)
200
250
300
350
0 400 800 1200 1600
Tem
p. (
ºC)
Time (Sec)
r = 7.75(270_deg)(2)
r = 12.25(2)
200
250
300
350
0 400 800 1200 1600
Tem
p. (
ºC)
Time (Sec)
theta = 0(2)
theta = 90(2)
r=7.75mm
Measured temperature at 1.5kWAir temperature: porous receiver outlet
200
250
300
350
400
0 600 1200 1800 2400 3000 3600
Tem
p.(
ºC)
Time(Sec)
r = 0,rec.2 r = 0,rec.3r = 0,rec.4 r = 0,rec.6r = 0, rec.7
POA = 1500 W, MFR = 5.04 g/s, POA/MFR = 300
xx
x
x
Maximum temperature is about 350 CAverage temperature is about 325 CVariation of about 7% is observed at the steady state
Evaluation of mixer
ɵ = 00
ɵ = 1800
ɵ = 00
ɵ = 900
ɵ = 1800
Z1Z5
Experiment 1 A B D
PoA (Watt) 750 750 1250 1250
Equivalent Concentration (Sun)
210 210 350 350
PoA/MFR (kJ/Kg) 100 200 200 300
125
150
175
200
225
250
0 100 200 300
Air
te
mp
era
ture
(ºC
)
Theta(ɵ)
Temp.(ºC) at Z1 (1) Temp.(ºC) at Z5 (2)Temp. at Z1(A) Temp. at Z5(A)Temp. at Z1(D) Temp. at Z5(D)Temp at Z1 (B) Temp at Z5 (B)
Z1: Non-uniform (azimuthal)
Z5: Uniform (mixing)
8 equally spaced TC
2
4
6
8
125
150
175
200
225
0 400 800 1200 1600
Tem
p. (
ºC)
Time (Sec)
Outlet 2 Outlet 4
Outlet 6 Outlet 8
Fig: Components of open air receiver (a), Position of T/C to measure the outlet temperature of air (b) Outlet air temperature (c)
ab
c
Temp. at location 4 is lower thanthe other because of heat lossdue to improper insulation
Efficiency performance curve
Efficiency deceases with temperature for any given powerLinearly decreasing trend of efficiency with PoA/MFR and outlet
temperature is observed (see e.g. Hoffschmidt et al. (2003)) A correlation, such as, Efficiency = f(power, mass flow rate,
temperature) will be derived
0
50
100
150
200
250
300
350
50
60
70
80
90
100
0 100 200 300 400 500
Ou
tlet
air
tem
p.(
ºC)
Effi
cien
cy (
%)
POA/MFR(kJ/kg)
Effciency(P=1250W) Efficiency (P=1500W)Effciency (P=1000W) Efficiency (P=750W)T_out(P=1250W) T_out(P=1500W)T_out(P=1000W) T_out(P=750W)
Show stopper!!!
Dust deposition Blockage Consequence??
Solution:- Removal;
- Cleaning;
- Collection;
Status: Design in progress
Conclusion
- The first design of volumetric air receiver is being evaluated
- Experiment and analyses indicate potential for application to process heat
- Cleaning strategy is under development
Other activities
Motivation and Objective
God plays Dice!! Sunny regions are usually blessed with dust
Dust deposition on heliostat Reduces reflectivity Consequences?? (surprise)
Objective: Understanding of the physics of deposition and analysis
Solar radiation Reflection towards
receiver
Sun Heliostat Central Receiver
How dust deposits and analysis procedure
Wind
Wind
Wind
Analysis of critical velocity for initiating saltation process
Velocity required to initiate the removal process:
Critical velocity require to lifting dust particle
ipipglgdd rFrFFrF
**)(*
Forces act on dust particles [1]
Condition for lifting dust particle [1]
2
1
'
2
3
6z
Ar
338
AC
gr
uda
p
Small dust size Higher Threshold Velocity More difficult to remove
Reference : [1] J. F. Kok, Eric J. R. Parteli, T. I. Michaels, and D. BouKaram,” The physics of wind-blown sand and dust ,” PACS:
47.55.Kf, 92.60.Mt, 92.40.Gc, 45.70.Qj, 45.70.Mg, 45.70.-n, 96.30.Gc, 96.30.Ea, 96.30.nd.
Acknowledgement
The R & D activities are funded and realized with support from:
Ministry of New and Renewable Energy (MNRE), Govt. of India
IIT Jodhpur, Ministry of Human Resource Development (MHRD), Govt. of India
All students and staff members
Pf = pressure of fluid (Pa) ρf = density of fluid (kg/m3) p = static pressure (Pa)
R = gas constant (J/kg K) Tf = temperature of fluid (K) k = turbulence kinetic
energy (J)
A = area (m2) S = source term (W/m3) τ = stress tensor (N)
Uf = velocity of fluid (m/s) CPf = Specific heat capacity of
fluid (J/KgK)
Es = total solid energy
(J)
Ts = temperature of solid (K) Ef = total fluid energy (J) R’ = (Rs/Rout)
λf = Thermal conductivity of
fluid (W/mK)
ε = porosity (%) T = mass averaged
temperature (K)
m = mass flow rate of air
(kg/m3)
RS = Radial position of the plate
opening (m)
DP = Diameter of pore
(mm)
λs = Thermal conductivity of
solid (W/mK)
λeff = effective thermal
conductivity
= ε λf + (1- ε) λs (W/mK)
Rout = radius at mixer
outlet (m)
Nomenclature