# Air Receiver - Explore the Science & Experts | ideXlab

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### Zhifeng Wang – One of the best experts on this subject based on the ideXlab platform.

• ##### Numerical investigation of the heat transport in a very loose packed granular bed AirReceiver with a non-uniform energy flux distribution
Renewable Energy, 2019
Co-Authors: Shengchun Zhang, Zhifeng Wang, Fengwu Bai, Pingrui Huang

Abstract:

Abstract This study analyzes the heat transfer of the solar energy absorbed by the porous media Receiver to Air where the porous media can reach temperatures up to 1000 °C. The heat transfer was studied numerically for a packed granular bed Air Receiver with a non-uniform energy flux distribution. The conduction is modeled as an effective thermal conductivity with the Ergun equation used to describe the pressure drop. The radiative heat transfer is modeled by a modified P-1 radiative heat transfer model. The local thermal non-equilibrium model is used to relate the Air temperatures to the porous media temperatures. Comparisons with experimental data show that this model can accurately predict the heat transfer in the packed granular bed Air Receiver. The model is used to analyze the effects of flow direction, gas mass flow rate per unit area, particle emissivity, estimated fractional contact area, and particle size. The results illustrate that downward flows, larger gas mass flow rates, higher particle emissivities, larger estimated fractional contact areas, and smaller particle sizes all enhance the heat transport and that the packed bed Receiver outlet Air temperature does not vary much for relatively short term fluctuations of the solar flux.

• ##### Experimental study of a heat pipe pressurized AirReceiver
SOLARPACES 2018: International Conference on Concentrating Solar Power and Chemical Energy Systems, 2019
Co-Authors: Shunzhou Chu, Fengwu Bai, Zhiying Cui, Fuliang Nie, Zhifeng Wang

Abstract:

This study investigated the startup characteristics and thermal performance of a heat pipe pressurized Air Receiver. The heat flux on the Receiver of around 130 kW/m2 was tested to be an appropriat…

• ##### Thermal analysis of honeycomb ceramic AirReceiver
, 2017
Co-Authors: Zhifeng Wang, Fengwu Bai, Shunzhou Chu, Bei Yang

Abstract:

This study investigated the heat transfer between Air flow and honeycomb ceramic Air Receiver. A one-dimensional model of the Receiver was established considering the distribution of the solar radiation within the channel and the radiative heat transfer between the inner surfaces. The sensitivity studies had been done to explore the influences of the absorber geometric parameters, the incident solar radiation and the Air flow rate on the Receiver steady-state thermal efficiency and outlet Air temperature. The minimal absorber length was analyzed to ensure high thermal efficiency, which is significant for the Receiver design and optimization.

### Laltu Chandra – One of the best experts on this subject based on the ideXlab platform.

• ##### a novel approach for modelling fluid flow and heat transfer in an open volumetric AirReceiver using ansys fluent
Solar Energy, 2020
Co-Authors: P Sharma, Laltu Chandra, P S Ghoshdastidar, R Shekhar

Abstract:

Abstract Open volumetric Air Receiver (OVAR) has great potential as a source of process heat for metals processing operations. The two major components of OVAR are the porous absorbers and the return Air flow chamber (RAFC). Heat exchange between the “cooler” return Air and the hot curved absorber surface in RAFC is critical as it prevents overheating of absorbers. Unfortunately, modeling of Air flow in the RAFC is conspicuous by its absence. Calculations were performed in ANSYS-FLUENT using the local thermal non-equilibrium model for heat transfer in the porous absorber. Three dimensional flow and heat transfer simulations were carried out in the RAFC. Unfortunately, ANSYS decoupled heat exchange between the absorbers and return Air by splitting the curved absorber surface into real and imaginary surfaces. Decoupling also meant that heat flux had to be specified separately on the absorber and the RAFC, which was a challenge since only the total input solar flux is known. Hence the major contribution of this paper has been to incorporate two innovations in the simulation methodology. One, to couple the absorber and RAFC thermally by mapping the temperature of the real surface to the imaginary surface. Two, the flux used for heating Air in the absorber was calculated iteratively. Limited simulations suggest that in laboratory experiments, relatively inexpensive circumferential (Joule) heating of absorbers can reasonably mimic heating of absorbers by concentrated solar radiation.

• ##### One-Dimensional Zonal Model for the Unsteady Heat Transfer Analysis in an Open Volumetric AirReceiver
Journal of Thermal Science and Engineering Applications, 2020
Co-Authors: Gurveer Singh, Rajiv Shekhar, Laltu Chandra, Vishwa Deepak Kumar, P S Ghoshdastidar

Abstract:

Abstract
The open volumetric Air Receiver (OVAR)-based central solar thermal systems provide Air at a temperature &gt; 1000 K. Such a Receiver is comprised of porous absorbers, which are exposed to a high heat-flux &gt; 800 Suns (1 Sun = 1 kW/m2). A reliable assessment of heat transfer in an OVAR is necessary to operate such a Receiver under transient conditions. Based on a literature review, the need for developing a comprehensive, unsteady, heat transfer model is realized. In this paper, a seven-equations based, one-dimensional, zonal model is deduced. This includes heat transfer in porous absorber, primary-Air, return-Air, Receiver casing, and their detailed interaction. The zonal model is validated with an inhouse experiment showing its predictive capability, for unsteady and steady conditions, within the reported uncertainty of ±7%. The validated model is used for investigating the effect of operating conditions and absorber geometry on the thermal performance of an absorber. Some of the salient observations are (a) the maximum absorber porosity of 70–90% may be preferred for non-volumetric and volumetric-heating conditions, (b) the minimum Air-return ratio should be 0.7, and (c) the smallest gap to absorber-length ratio of 0.2 should suffice. Finally, suggestions are provided for extending the model.

• ##### on the flow stability in a circular cylinder based open volumetric AirReceiver for solar convective furnace
Energy Procedia, 2018
Co-Authors: G P Singh, Laltu Chandra

Abstract:

Abstract The arid desert regions are considered for installing the concentrated solar thermal based systems owing to the available direct normal irradiance. For process heat applications, like the solar convective furnace that requires an Air temperature of 750 K the open volumetric Air Receiver is preferred. Such innovative concepts are envisaged for achieving high thermal energy conversion efficiency. For the prolonged operation of the solar convective furnace system the stable flow is necessary. On the other hand, the thermally induced flow instability is reported in the open volumetric Air Receivers at a high temperature. This may limit the operating temperature range of a Receiver. In this paper the flow stability analysis in a circular cylinder based open volumetric Air Receiver with the straight pores is presented. The findings allow expecting a stable flow regime in such an absorber pore at a high flux concentration and temperature.

### R Shekhar – One of the best experts on this subject based on the ideXlab platform.

• ##### a novel approach for modelling fluid flow and heat transfer in an open volumetric AirReceiver using ansys fluent
Solar Energy, 2020
Co-Authors: P Sharma, Laltu Chandra, P S Ghoshdastidar, R Shekhar

Abstract:

Abstract Open volumetric Air Receiver (OVAR) has great potential as a source of process heat for metals processing operations. The two major components of OVAR are the porous absorbers and the return Air flow chamber (RAFC). Heat exchange between the “cooler” return Air and the hot curved absorber surface in RAFC is critical as it prevents overheating of absorbers. Unfortunately, modeling of Air flow in the RAFC is conspicuous by its absence. Calculations were performed in ANSYS-FLUENT using the local thermal non-equilibrium model for heat transfer in the porous absorber. Three dimensional flow and heat transfer simulations were carried out in the RAFC. Unfortunately, ANSYS decoupled heat exchange between the absorbers and return Air by splitting the curved absorber surface into real and imaginary surfaces. Decoupling also meant that heat flux had to be specified separately on the absorber and the RAFC, which was a challenge since only the total input solar flux is known. Hence the major contribution of this paper has been to incorporate two innovations in the simulation methodology. One, to couple the absorber and RAFC thermally by mapping the temperature of the real surface to the imaginary surface. Two, the flux used for heating Air in the absorber was calculated iteratively. Limited simulations suggest that in laboratory experiments, relatively inexpensive circumferential (Joule) heating of absorbers can reasonably mimic heating of absorbers by concentrated solar radiation.

• ##### experimental and computational investigation of heat transfer in an open volumetric AirReceiver for process heat application
, 2018
Co-Authors: P Sharma, Laltu Chandra, R Shekhar, P S Ghoshdastidar

Abstract:

India receives abundant solar irradiance with an annual average of ~19.97 MJ/m2 per day in Jodhpur only. This solar energy can be harnessed for electricity generation, melting or heat treatment of metals. Use of Air as heat transfer fluid offers significant advantages of being nontoxic, freely available and operating temperature beyond 800 °C. Considering these aspects, as a research initiative, open volumetric Air Receiver (OVAR) is being developed with a peak-power capacity of 4 kWth. The installed testing facility at IIT Jodhpur includes sub systems, which are thermal energy storage (TES), Air–water heat exchanger. In the absence of solar simulator electrical heating is being employed for circumferential (external) heating of the absorbers. In particular, the presented paper presents:

(a)

Effect of pore diameters (2 and 3 mm) on the average outlet temperature of absorber with porosity (Ɛ) ~52% at $${\text{POA/MFR}} = 100\;{\text{kJ/kgK}}$$, where POA is the equivalent Power-On-Aperture and MFR is mass-flow rate of Air;

(b)

Efficiency performance curve for absorbers with Ɛ ~ 52%;

(c)

Modeling of heat transfer in absorber with adopted commercial CFD tool FLUENT including returned Air circulation;

(d)

Comparison between CFD analyzed and experimentally obtained temperature for absorbers with Ɛ ~ 42, 52, and 62%;

(e)

Predictions with incident radiation onto the front surface of porous absorber.

• ##### design of a cyclone separator for cleaning of dust from volumetric AirReceiver
, 2017
Co-Authors: G P Singh, Laltu Chandra, Dheeraj Saini, R Shekhar

Abstract:

Arid regions, like Rajasthan, receive abundant solar energy and are prone to dust/sand storms. Line and point focusing technologies are used for harnessing this energy. At IIT Jodhpur, open porous volumetric Air Receiver based point focusing technology is considered for process heat application. This system uses Air as heat transfer fluid and is expected to achieve a temperature as high as 800 °C. This Receiver on account of volumetric heating, is exposed to a high heat flux, even, up-to 1000 suns (1sun = 1 kW/m2). As this Receiver is open to atmosphere, the dust storms in these regions can block the absorber pores and enter the system. Due to lower thermal conductivity of sand in comparison to absorber material, high temperature gradients and thermal stresses are expected on the absorber. It can result in failure of the system. In view of this the current activity aims at cleaning and collection of the removed dust from pores of Receiver. A 2D2D geometry of cyclone separator is proposed for deposited dust collection. The experiments on collection efficiency and pressure drop are performed and compared with empirical model. Pressure drop is estimated using CFD and experimentally validated for an improved relation for pressure drop coefficient.