نشریه انرژی ایران
سال نهم شماره 1 (پیاپی 33، آبان 1383)

Adaptive thermal comfort usually decreases energy consumption in residential buildings. For adaptive thermal comfort there should be established a relation between indoor and outdoor design temperatures. Natural ventilation (N.V) is one of the methods to achieve this condition. In buildings with hydronic floor heating systems thermal inertia is significant. In such cases it is difficult to conform to working fluid temperature with outdoor design temperature. So adjust clothing plays a main role to bring adaptive thermal comfort condition in residential buildings with floor heating system. This study is focused on influence of thermal structure of building on adaptive thermal comfort. In hydronic floor heating systems thermal structure of building and adaptive thermal comfort are independent. In these systems, small increase in cloth insulation (0.2 Clo), causes 5% decreasing in energy consumption.

Retrofit design of heat exchanger networks using Pinch technology is mainly applied for two reasons; improvement of a network for energy saving as well as improvement of a network with new flow rate in its process streams. The latter is called Retrofit for Debottlenecking of the Heat exchanger Network. All networks about which retrofit design have been studied so far follow methods rather than those in pinch technology. Regarding changes in process industries to respond to market design, factories have to expand their throughput, so pinch technology as a strong tool can be used in such situations, as there would be new changes in process structure along with undesired restrictions. It, also, can be true for networks the grassroots design of which was based on pinch technology for a premier throughput. In this research, we considered a heat exchanger network designed using Pinch Technology Method whose throughput is going to increase. After investigating the conditions of the network and predicting what changes would happen, the optimum method was introduced to target the final results of the design step in a way that not only network restrictions will be overcome, but also will network be able to work with the economical conditions. Finally, a case study of an Aromatic plant was applied to illustrate targeting and design step results. These results verify the proposed method of Pinch Technology in the retrofit design for debottlenecking of heat exchanger networks designed by PDM.

It is important to predict energy demand and its variations, in order to plan for enough energy supply. Daily utilization duration of electric devices is considered as an effective factor, by which the total energy consumption is obtained. This paper studies the impact of climate on that variable. First, an experimental function is introduced, which explains the relationship between the temperature and the electrical energy consumption. Thereafter, effect of that variable on the Average Daily Utilization Duration is investigated through a set of parallel linear models, in companion of other factors. The electricity price index, other fuel price indexes, per capita income and a dummy variable for some historical facts form different terms of the linear models. The results obtained by a fuzzy decision making method, show that about one half of the average time in daily utilization of the electrical devices is affected by the climate variation.

Using numerical method for heat transfer is cheaper than experimental methods. In this articles heat transfer in solid plate with difference materials has been analyzed. Computation times and the accuration of solving problems have been compared in difference numerical methods. This problem has been solved with general finite difference method in three form of implicit, explicit, Crank Nickolson by a code, which is written by FORTRAN 90. Tecplot is used to view the results such as temperature distributions. The problem has been solved by finite volume software such as fluent and finite element software such as ansys to compare and test the results driven from FORTRAN code. In finite volume method the velocity and pressure fields in steady state form has been solved. Momentum equations in x,y directions has been solved by first order upwind and the continuity and energy equations has been solved by first order upwind method. The finite element problem has been solved by using a 2-D, 8-node thermal element. The element has one degree of freedom, temperature, at each node. The 8-node elements have compatible temperature shapes and are well suited to model curved boundaries. Convection or heat flux (but not both) and radiation may be input as surface loads at the element faces. In general, comparison the finite volume method has the better results in comparison with the others method such as finite difference or finite elements also the finite element method is better than finite difference method for predicting the heat transfers in a 2dcomposite block. In finite difference (Explicit) by refining mesh concentration, the computational time has been reduced but increasing mesh concentration for reducing the computational time has a limit and after passing this limit the computational time will be constant. Computational time will be reduced by using the explicit method in comparison of the Crank Nickolson method. An implicit method shows the better Temperature distribution near the boundary in comparison with two other methods. Difference form of finite difference method (implicit, explicit, Crank Nickolson) shows equal temperature distribution far from the boundary limits

The purpose of this study is to find a maximum work output from various combinations of Thermodynamic cycles from a viewpoint of the cycle systems. Three systems were discussed in this study a fundamental combined cycle and two other cycles evolved from the fundamental dual combined cycle series-type and parallel-type triple cycles. In each system, parametric studies were carried out in order to find optimal configuration of cycle combinations based on the influences of tested parameters on the systems. The study shows that the series-type triple cycle exhibits no significant difference as compared with the combined cycle. On the order hand. the efficiency of the parallel-type triple cycle can be raised, especially in the application of recovering low-enthalpy-content waste heat Therefore by properly combining with a steam Rankine cycle, the organic Rankine cycle is expected to efficiently utilize residual yet available energy to an optimal extend. The present study has pointed out a conceptual design in multiple-cycle energy conversion Systems