Numerical simulation model of solar air heater using ansys-14

Thermal performance of downward- type single-pass flat plate solar air heater (SAH) with pin fins attached on absorber plate are investigated numerically. Calculations of outlet air temperature and collector efficiency have been done with and without application of recycling operation. Numerical simulation of solar air heater has been performed by the use of ANSYS-14 (FLUENT) software. 196 square pin fins on absorber plate has been attached and by maintaining both the pitch lengths (transverse and longitudinal) constant optimization of fin height and thickness (side) has been done for various values mass flow rates and results are represented in graphical as well as tabular form. The effects of in-line and staggered arrangements of fins on the performances of solar heater have been compared. It is found that due to the application of pin fins, with a mass flow rate of 0.02 kg/s, thermal efficiency of solar air heater increases upto 99% and 91% for staggered and in-line arrangements respectively, as compared to SAH operating without fins with same air flow rate. The results showed that SAH with staggered arrangement is upto 13%, 6.5% and 4.5% more efficient than in-line arrangement with a mass flow rates 0.05, 0.01, 0.02 kg/s respectively.
  1. Introduction
Man has needed and used energy at an increasing rate for his sustenance and well-being ever since he came on the earth a few million years ago. Primitive man required energy primarily in the form of food. He derived this by eating plants or animals which he haunted. Subsequently he discovered fire and his energy needs increased as he started to make use of wood and other biomass to supply the energy needs for cooking as well as for keeping himself warm. With the passage of time, man started to cultivate land for agriculture. He added a new dimension to the use of energy by domesticating and training animals to work for him. With further demand for energy, man began to use the wind for sailing ships and for driving windmills, and the force of falling water to turn water wheels. Till this time, it would not be wrong to say that the sun was supplying all the energy needs of man either directly or indirectly.
The industrial revolution which began with the discovery of the steam engine (AD1700) brought about a great many changes. For the first time, man began to use a new source of energy, viz. coal, in large quantities. A little later, the internal combustion engine was invented (AD 1870) and the other fossil fuels, oil and natural gas began to be used extensively. The invention of heat engines and use of fossil fuels made energy portable and introduced the much needed flexibility in man’s movement. For first time, man could get the power of a machine where he required it and was not restricted to a specific site like a fast-running stream for running a water wheel or a windy hill for operating a windmill. This flexibility was enhanced with the discovery of electricity and the development of central power generating stations using either fossil fuels or water.
A new source of energy-nuclear energy- came on the scene after the Second World War. The first large nuclear power station was commissioned about 70 years ago and now these days, nuclear energy is providing a significant amount of the energy requirements of many countries.
  • The production oil reached a maximum around 1985 and now is declining. Present indications are that most of the reserves of oil and natural gas are likely to be consumed in other 40 year.
  • As oil and natural gas become scarcer, a greater emphasis will fall on coal. It is likely that the production of coal will touch a maximum somewhere between the years 2030 and 2060 and that 80 per cent of the amount available could consumed by 2250 AD.
1.1 Introduction to solar air heater with recycle
It is a particular type of solar air heater in which some amount of heated air from the outlet of air heater is continuously circulated through recycle channel and it is re-mixed to the fresh air at the inlet. Due to recycling the temperature and flow rate of air get increased at inlet. The ratio of rate at which air is circulated through recycle channel to the rates at which air is collected at outlet is called recycle ratio or reflux ratio (R). A schematic diagram of recycle type solar air heater is shown in fig.1.
It was pointed out that applications of the recycle effect in the design and operation of the equipment with external or internal reflux can effectively enhance the effect on heat- and mass-transfer, leading to improved performance [5-8]. Actually, there are two conflict effects of recycle operation. One is the desirable effect of increasing fluid velocity, resulting in enhancement of convective heat- or mass-transfer, while the other is the undesirable effect of decreasing the driving force (temperature or concentration difference) due to remixing. It was found that the increase in convective heat- or mass-transfer by increasing the reflux ratio can generally compensate for the decrease of driving force, leading to improved performance.
  1. Numerical simulation and analysis
Numerical Simulation in a crude sense is the method of predicting the output of a proposed system or an existing system without conducting experiment on it. A commercially available software ANSYS-14.0 (FLUENT) is used to investigate the thermal performance of solar air heater with pin fins attached on absorber plate.
  1. Steps for Simulation in Computer Aided Engineering Software (CAE)
Simulation in CAE software contains three main steps and various sub-steps
  • Pre-Processing
This is the first step of CFD simulation process, which helps in describing the geometry in the best possible manner. It has some sub-steps as follows
  • Generation of geometry
  • Grid generation
  • Physics model selection
  • Material properties
  • Boundary condition
  • Initial condition
  • Solver
Once the problem physics has been identified, fluid material properties, flow physics model, and boundary conditions are set to solve using computer through following processes
  • Solver selection
  • Residual target
  • Initialization
(c) Post Processing
The next step after getting the results is to analyze the results with different methods like contour plots, stream lines, vector plots etc.
  1. Geometry Generation

The collector consists of one glass cover (2 mm thickness), a black absorber plate (0.6 x 0.6 m), 196 square shape pin fins of aluminum attached on absorber plate, one channel of dimensions (0.6 x 0.6x 0.05 m) for downward flow of air and an insulated recycle channel of same dimensions as shown in fig. 2. The air flows in passage between glass cover and absorber plate and some amounts of hot air from outlet is re-circulated through recycle channel and it is re-mixed with cold air at inlet of SAH.


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This article is published in peer review journal and open access journal, International journal of research in engineering and innovation (IJREI) which have a high impact factor journal for more details regarding this article, please go through our journal website.



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