A review of information flow diagrammatic models for product–service systems

Quality of an assembly of any manufactured product is mainly based on the quality of mating components. Due to random variations in sources such as materials, machines, operators, and measurements, mating components manufactured by even the same process may vary in their dimensions. When mating components are assembled linearly, the resulting assembly tolerance will be the sum of the mating components tolerances. All precision assemblies demand for a closer assembly tolerance. A significant amount of research has already been done to minimize assembly variation using selective assembly, when the dimensions of components follow normal distribution. However, in reality, the dimensions of components produced especially in smaller to medium size batches, invariably have some skewness (non-normality), which makes the methods developed and reported in the literature, often not suitable for practice. In this work, batch selective assembly methodology is proposed for components having non-normal distributions to minimize the assembly tolerance variations. The proposed method which employs a genetic algorithm for obtaining the best combination of mating components is able to achieve minimum variations in assembly tolerances and also maximum number of acceptable assemblies. The proposed algorithm is tested with a set of experimental problem datasets and is found outperforming the other existing methods found in the literature, in producing solutions with minimum assembly variation.     

Role of Nano-YbF3-Treated Carbon Fabric on Improving Abrasive Wear Performance of Polyetherimide Composites

A method for surface treatment of carbon fabric with nano-particles of rare earth salt (ytterbium fluoride–YbF₃) was tried first time in the authors’ laboratory to enhance the fiber–matrix interface, and has been reported here. In this article authors have reported on the performance evaluation of composites developed from the four fabrics treated with various doses viz. 0, 0.1, 0.3, and 0.5 wt% of YbF₃. The abrasive wear performance of these composites was evaluated by abrading the composites against silicon carbide abrasive paper under varying loads. The treated fabric composites exhibited lower coefficient of friction and higher wear resistance as compared with untreated fabric composite. A linear correlation between ILSS (interlaminar shear strength) and wear resistance was observed. Both were the highest for 0.3% dosing of fabric. Since it was also desirable to compare the efficiency of this novel method of treatment of carbon fibers with conventional one, a few results of composites with plasma-treated carbon fabric were compared with the nano-particle-treated fabric composites. It was concluded that the latest method improved the abrasive wear resistance of composites almost two times more than the plasma-treated composites. Fiber–matrix interface was strengthened because of the treatment as observed from SEM studies, ILSS, and matrix pick-up studies. Increased roughness of fiber surface was observed in topographical analysis by SEM. Effect of treatment on fiber was also observed by adhesion test and fiber tow tension test. SEM studies of worn surfaces were performed to understand wear mechanisms.     

Parametric study of various configurations of hybrid PV/thermal air collector: Experimental validation of theoretical model

In this paper, an attempt has been made to evaluate the overall performance of hybrid PV/thermal (PV/T) air collector. The different configurations of hybrid air collectors which are considered as unglazed and glazed PV/T air heaters, with and without tedlar. Analytical expressions for the temperatures of solar cells, back surface of the module, outlet air and the rate of extraction of useful thermal energy from hybrid PV/T air collectors have been derived. Further an analytical expression similar to Hottel–Whiller–Bliss (HWB) equation for flat plate collector has also been derived in terms of design and climatic parameters. Numerical computations have been carried out for composite climate of New Delhi and the results for different configurations have been compared. The thermal model for unglazed PV/T air heating system has also been validated experimentally for summer climatic conditions. It is observed that glazed hybrid PV/T without tedlar gives the best performance.     

Analytical expression for thermal efficiency of a passive solar still

Using energy balance equations for the different components of a passive solar still (namely, glass cover, water mass and basin liner), the effect on its thermal efficiency of water flowing over the glass cover with uniform velocity has been studied analytically. The efficiency is found to increase due to the water flow at higher depths of water in the basin. The result is validated by the experimental results of other authors.     

Parametric study of a reverse flat plate absorber cabinet dryer: A new concept

In this communication, the concept of reverse flat plate collector has been used as a heating medium of air for the drying of agricultural products in a cabinet dryer. The reverse flat plate absorber is a non-concentrating collector which can collect solar heat at high temperature unlike conventional nonconcentrating collectors. The thermal performance of the proposed dryer is analyzed by solving the various energy balance equations. An attempt has been made to optimize the vent area of the dryer for speedy flow of humid air from the drying chamber to the atmosphere. In order to have parametric studies, numerical computations have been carried out for a typical day in June for Delhi climatic conditions. The performance of this system is compared with that of conventional cabinet dryers. It is found that the reverse flat plate absorber dryer gives the better performance.     

Thermal performance of ground as an inexpensive solar collector and storage system

This paper presents an analysis of the performance of an inexpensive integrated solar collector and storage system. The flow of fluid and heat capacity of the storage material in the container is considered simultaneously and an evaluation is made for the resulting outlet fluid temperature for various flow rates and materials by solving the Fourier heat conduction equation with appropriate boundary conditions in different regions. This evaluation, combined with energy balance considerations, yields an expression for the transient rate at which heat can be retrieved—by keeping flow rate constant. Numerical calculations, corresponding to a typical winter day in Delhi have been carried out. The heat retrieval efficiencies are of the order of 50-25%. A phase difference of about 12–18 h is obtained between the maxima of solair temperature and outlet water temperature. The efficiency of the system increases with flow rate and decreases with depth of plane of heat retrieval. Concrete is found to be the best inexpensive sensible heat storage material out of those materials considered.     

Heat transfer enhancement in cross-flow heat exchangers using oval tubes and multiple delta winglets

A three-dimensional study of laminar flow and heat transfer in a channel with built-in oval tube and delta winglets is carried out through the solution of the complete Navier-Stokes and energy equations using a body-fitted grid and a finite-volume method. The geometrical configuration represents an element of a gas-liquid fin-tube cross-flow heat exchanger. The size of such heat exchangers can be reduced through enhancement of transport coefficients on the air (gas) side, which are usually small compared to the liquid side. In a suggested strategy, oval tubes are used in place of circular tubes, and delta-winglet type vortex generators in various configurations are mounted on the fin-surface. An evaluation of the strategy is attempted in this investigation. The investigation is carried out for different angles of attack of the winglets to the incoming flow for the case of two winglet pairs. The variation of axial location of the winglets is also considered for one pair of winglets mounted in common-flow-down configuration. The structures of the velocity field and the heat transfer characteristics have been presented. The results indicate that vortex generators in conjunction with the oval tube show definite promise for the improvement of fin-tube heat exchangers.     

Economic analysis of a G.I. sheet multiwick solar distillation plant

On account of the energy crisis, several types of solar energy devices have been developed and marketed in various parts of the world with varying degrees of thermal performance. The economic aspect of these solar energy devices becomes more significant when they replace those devices which use conventional fuels. In this paper, an economic analysis of one of the solar energy devices, namely a G.I. sheet multiwick solar distillation plant, has been presented taking into account the various factors, viz. the lifetime of the system, salvage values of the system, interest rate and maintenance cost.     

Transient analysis of double basin solar still

The effect of water flowing over the upper glass cover of a double basin solar still on its transient performance has been presented. A comparative study of the daily distillate production of a double basin solar still with and without water flowing over the upper glass cover has been made, and some interesting conclusions have been drawn. Numerical calculations have been made for a typical hot day (viz 2 May 1980) in Delhi.     

Demonstration plant of a multi wick solar still

A solar distillation plant of capacity 70 litres/day (annual average) has been installed at the Centre of Energy Studies, Indian Institute of Technology, New Delhi, India. The system has been working for the last 1 year, and its performance is found to be satisfactory. It meets the requirements of distilled water in the Institute.