جستجوی مقالات مرتبط با کلیدواژه "پمپ حرارتی" در نشریات گروه "مکانیک"

Energy consumption in the Iran’s food industry is mainly through fossil fuels (natural gas, electricity). In the food industry, the most use of natural gas is related to boilers and the most use of electricity is related to the refrigeration system. Due to of this issue to save energy in this particular field, many studies have been done. One of the cases that can be used is the use of renewable energy. The purpose of this study is to review the use of this type of energy to provide all or part of the heating and cooling system and the rules relations governing the user of this kind of energy, which can be good supplements for optimal energy consumption in boilers and thermodynamic cycles. Also, to make useful usage of heat and energy wasted, the CCHP can be used and heat pumps with a renewable source to produce heat with high temperature from natural source. The results showed that if the combine of cooling, heating and power system along with solar energy can be used to operate the heat pump, despite the high initial cost, it can have a significant improvement in energy consumption and cost.

In this research, the modeling of a solar renewable system along with the use of intelligent optimization method was discussed in order to increase the system performance and reduce the life cycle cost. A system with a combination of five units of PVT panel, heat pump, PEM electrolyzer, hot water storage source and fuel cell was designed to provide the required energy consumption of an 80-unit residential complex in Iran, including hot water, cooling, heating and electricity. The performance of the proposed system was analyzed by using the weather information of the coastal city of Bandar Lengeh in Hormozgan province. System modeling was done using a new approach by TRNSYS software. Optimization of this system to increase system performance and reduce life cycle cost was done by Design Expert software and using RSM. The three objective functions investigated included electricity production, PMV and LCC, and four decision variables including the number of solar panels, fuel cell capacity, heat pump capacity and electrolyzer capacity were selected. The optimization results showed that in the most optimal state with the number of 1425 solar panels, the capacity of 65.99 kW for the fuel cell, the capacity of 40.01 kW for the heat pump and the capacity of 52.5 kW for the electrolyzer are in the optimal state. The system can reach the production value of 725955.25 kWh per year in the optimal condition with a PMV of 0.43 and a LCC of 344014.63 $.

In the current research, a renewable system based on wind, solar, and geothermal energy was analyzed with a targeted combination of fuel cell units, heat pump, proton exchange membrane electrolyzer, steam turbine and reverse osmosis. Transient modeling and simulation of the proposed system was done using TRNSYS software. This system was designed and evaluated to meet the needs of a residential complex with 80 residential units and 320 people for electrical energy, cooling, and heating. A case study was conducted for the feasibility of setting up the proposed system in the coastal city of Bandar Anzali in Iran. Optimization of system performance was done by determining two objective functions of production power and system life cycle cost with response surface method and Design Expert software. Five parameters affecting the system performance including the number of wind turbines, number of solar panels, fuel cell capacity, steam turbine capacity, and proton exchange membrane electrolyzer capacity were selected as optimization variables. In its most optimal state, the system can reach a production power of 3036105.022 kWh and a life cycle cost of 781944.254 $. The environmental results showed that by setting up the system in an optimal mode in Bandar Anzali city and producing electricity at the rate of 3036.1 MW per year, it is possible to help expand 3 hectares of green space per year. It also helped reduce carbon dioxide emissions by 619.36 tons of CO2 at a cost of 14,864.74 $.

A great amount of global energy is consumed for building heating and cooling. Renewable energies are considered to prevent pollution made by fossil fuel in the building industry. Ground source heat pumps are known as a technology to supply heating and cooling demand in buildings. In this paper, the energy demand for residential cooling and heating is calculated in Iran in 2030. Then, two scenarios are discussed to supply the needed energy. In the first scenario, the energy is supplied by air source heat pumps (split units), and the second scenario considered ground source heat pumps. The result indicates that not only the second scenario can cause 8736.7 million cubic meters of natural gas and prevent 59.6 million tonnes of air pollutants, but also the country can export 7028 million $ electricity to its neighbors. Also, the total cost for the country to supply the energy need is reduced by 49994 million dollars.

Recently, renewable energies have attracted attentions among different societies due to the reduction of fossil fuels resources and environmental problems. Geothermal energy has taken a particular consideration due to its permanent potential, as well as low operating costs and high efficiency. Nowadays, one of the most useful applications of geothermal energy is the geothermal heat pumps that use electricity to provide the cooling and heating demand of buildings. This system reduces the fossil fuel consumption, decrease external costs and government subsidies on fossil fuels. In this paper, Shiraz under construction building in 2015 is considered to evaluate the replacement of geothermal heat pumps with conventional systems. The result showed that by this method, annually 25’997’236 m3 of natural gas is saved, and approximately 8.7 million dollars is obtained by exportation, as well as the release of 208.5 thousand tons of pollutants to the environment is prevented. It was also observed that if the government allocates citizens 30 percent of heat pump costs as a subsidy, the government capital will return in 5 years.

The Aquifers are underground porous formations containing water. Confined aquifers are surrounded by impermeable layers on top and bottom, called cap rocks and bed rocks. These aquifers are suitable for seasonal thermal energy storage.A confined aquifer with a very low groundwater flow velocity was considered to meet the annual cooling and heating energy needs of a residential complex located in Tehran, Iran.Three different alternatives of aquifer thermal energy storage (ATES) were employed to meet the heating/cooling demands of the complex. These alternatives were: using ATES for cooling alone, employing flat plate solar energy collectors for heating alone and employing a heat pump for cooling and heating. For the economical evaluation of the alternatives, a life cycle cost analysis was employed. For the environmental evaluation, Ret Screen software was employed. For the three considered operational alternatives, using ATES for cooling alone had the minimum payback period time of 2.41 year and life cycle cost of $16000. In the environmental consideration of the three alternatives, coupling of ATES with heat pump for cooling and heating had the minimum of CO2 generation, corresponding to 359 tons/year.

In variable refrigerant flow (VRF) heat pumps facing variable environmental conditions, the required load is achieved by means of compressor speed and expansion valve opening. Thus, this type of heat pumps is under transient conditions in addition to steady state conditions. Thus a detailed modeling is essential for an appropriate heat pump analysis and strategy. In the present paper, dynamic modeling of a VRF heat pump is conducted. For this purpose, dynamic modeling of heat exchangers is done via modified moving boundary method. Compressor and expansion valve are modeled in steady state as their thermal transient conditions are much faster compared to heat exchangers. Finally components models are coupled in MATLAB software. Validations indicate the present model with 5.3 percent error is more accurate than the previous studies (10 percent error). By investigating of compressor speed and expansion valve opening variations effect by the present model, it is concluded that transient conditions on system performance such as COP and generation are very effective compared to steady state conditions and these effects depend on the type and size of variation and in this article 15 percent difference is achieved. These conditions must be considered in system strategy, otherwise system real generation and model prediction will be different and consequently thermal comfort will be disturbed. Thus an accurate dynamic model is necessary for all steady and transient conditions and the present model can be utilized.

In this study, a solar assisted heat pump dryer with in direct model of evaporator- collector has been evaluated. The effective output parameters of the cycle are the coefficient of performance and the specific moisture extraction rate. In addition, the influence of different factors including condenser temperature, relative humidity of ambient air, slope angle of collector and temperature of evaporator on these parameters have been studied. For calculation of absorbed heat radiation in collector, the existing average temperature and the average daily radiation on a horizontal surface has been used. In direct expansion cycles, the absorbed heat by the collector in the evaporator case, vaporizes liquid refrigerant phase in the saturated gas phase. In this system, evaporator element is collector case, as well as the coils of evaporator. An element of collector can be used for two the first one is the absorbing heat and increasing temperature and the second the ability to be used as evaporator. In this study, a flat collector is used to absorb heat. The purpose of this study is to investigate promoting thermodynamic operation coefficient of entire cycle and humidity separation rate. The results of this study is capable of being evaluated for average radiation rate of Birjand, Tehran and Shiraz. This study also can be used for different refrigerants. The results show that the coefficient of performance of R134a refrigerant is 24% and 20%higher than R410a and R407c respectively.

Optimal design of combined renewable energy systems for supplying heat load of greenhouses is studied. It is tried to analyze the system technically and economically so that it would be optimal from both viewpoints. Optimal design is done from technical point of view using TRNSYS software by setting different parts of the system so that besides preheating of the fluid entering the evaporator of the heat pump for increasing the temperature, heat recovery of the ground in maximum heat extraction periods and heat recovery during summer time is occurred. The optimized system is then studied from economical point of view and the final optimized design is then selected by trade-off between economical and technical considerations. Selected model has mean seasonal coefficient of performance of 4.14 for heat pump, borehole length of 150 meters and total solar collector area around 9.42 square meters and the temperature of the fluid in ground cycle would increase up to 0.5 or 1 degrees centigrade. Optimal amounts gained are compared with those obtained from and TRNSYS and MATLAB relation. Finally to supply electrical load homer software is used and the optimum system is chosen considering design conditions.

Heat pumps are under variable loads in heating and cooling mode and their capacity must be controlled with respect to load. One of the best methods for heat pump control capacity is variable refrigerant flow (VRF) system. VRF heat pumps face complex dynamic conditions because of variable loads and interaction between heat pump and building, thus an appropriate heat pump modeling is essential for performance evaluation and utilization in control strategy fields. In the present paper, a study and comparison of VRF heat pump dynamic models to find an appropriate model for utilization in control strategy fields is performed. Among the available models, moving boundary model has high computation speed but lower accuracy and is not applicable sometimes such as start time. Finite difference model computation speed is low but its accuracy and stability is high. A combination of moving boundary and finite difference method (hybrid model) provides advantages in terms of model speed and accuracy as well as possibility to utilize in all dynamic and steady conditions. Besides, using this model in control strategy fields will result in appropriate performance, less building temperature fluctuations and less system energy consumption.

The operation of a novel solar-energized long term storage system has been studied using computer simulation. The system uses a phase change material (PCM) consisting CaC12، 6H20 for short-term heat storage; crushed-rocks sensible heat storage bin with enclosed hot water tank and heat pump system for medium-term heat storage، and soil for long-term heat storage. Calculations indicate that this system will provide a higher heat gain than a single bin system studied earlier. The single bin system was studied analytically and theoretically، comparing the use of a PCM and crushed-rocks، and included a heat pump operating from the same bin. Due to analysis and design method of experiment، the effect of six variance factors on system performance for higher PCM efficiency was studied.

I‌n r‌e‌c‌e‌n‌t y‌e‌a‌r‌s, d‌u‌e t‌o i‌n‌t‌e‌r‌n‌a‌t‌i‌o‌n‌a‌l e‌n‌e‌r‌g‌y a‌n‌d e‌n‌v‌i‌r‌o‌n‌m‌e‌n‌t‌a‌l a‌s‌p‌e‌c‌t‌s, t‌h‌e‌r‌m‌o‌a‌c‌o‌u‌s‌t‌i‌c‌s h‌a‌v‌e g‌a‌i‌n‌e‌d i‌n‌t‌e‌r‌e‌s‌t b‌y b‌e‌i‌n‌g c‌o‌n‌s‌i‌d‌e‌r‌e‌d a‌s a‌n a‌l‌t‌e‌r‌n‌a‌t‌i‌v‌e t‌e‌c‌h‌n‌o‌l‌o‌g‌y f‌o‌r r‌e‌n‌e‌w‌a‌b‌l‌e e‌n‌e‌r‌g‌y u‌t‌i‌l‌i‌z‌a‌t‌i‌o‌n. T‌y‌p‌i‌c‌a‌l t‌h‌e‌r‌m‌o‌a‌c‌o‌u‌s‌t‌i‌c s‌y‌s‌t‌e‌m‌s d‌e‌a‌l w‌i‌t‌h t‌h‌e c‌o‌n‌v‌e‌r‌s‌i‌o‌n o‌f h‌e‌a‌t e‌n‌e‌r‌g‌y t‌o s‌o‌u‌n‌d e‌n‌e‌r‌g‌y a‌n‌d v‌i‌c‌e v‌e‌r‌s‌a. T‌h‌i‌s p‌h‌e‌n‌o‌m‌e‌n‌o‌n d‌a‌t‌e‌s b‌a‌c‌k m‌o‌r‌e t‌h‌a‌n a c‌e‌n‌t‌u‌r‌y. R‌e‌c‌e‌n‌t a‌d‌v‌a‌n‌c‌e‌s i‌n t‌h‌e f‌i‌e‌l‌d o‌f t‌h‌e‌r‌m‌o‌a‌c‌o‌u‌s‌t‌i‌c‌s h‌a‌v‌e a‌l‌t‌e‌r‌e‌d t‌h‌e w‌o‌r‌k‌i‌n‌g m‌e‌c‌h‌a‌n‌i‌s‌m o‌f m‌a‌n‌y c‌o‌n‌v‌e‌n‌t‌i‌o‌n‌a‌l h‌e‌a‌t‌i‌n‌g a‌n‌d c‌o‌o‌l‌i‌n‌g d‌e‌v‌i‌c‌e‌s. T‌h‌e‌r‌m‌o‌a‌c‌o‌u‌s‌t‌i‌c s‌y‌s‌t‌e‌m‌s h‌a‌v‌e t‌h‌r‌e‌e d‌i‌s‌t‌i‌n‌c‌t‌i‌v‌e a‌d‌v‌a‌n‌t‌a‌g‌e‌s: f‌i‌r‌s‌t, t‌h‌e‌y a‌r‌e s‌i‌m‌p‌l‌e i‌n s‌t‌r‌u‌c‌t‌u‌r‌e, h‌a‌v‌e n‌o m‌o‌v‌i‌n‌g p‌a‌r‌t‌s, a‌n‌d h‌a‌v‌e l‌o‌w m‌a‌n‌u‌f‌a‌c‌t‌u‌r‌e c‌o‌s‌t‌s w‌i‌t‌h h‌i‌g‌h r‌e‌l‌i‌a‌b‌i‌l‌i‌t‌y; s‌e‌c‌o‌n‌d, b‌y u‌s‌i‌n‌g i‌n‌e‌r‌t g‌a‌s‌e‌s a‌s a w‌o‌r‌k‌i‌n‌g f‌l‌u‌i‌d, t‌h‌e‌y a‌r‌e e‌n‌v‌i‌r‌o‌n‌m‌e‌n‌t‌a‌l‌l‌y f‌r‌i‌e‌n‌d‌l‌y, a‌n‌d; f‌i‌n‌a‌l‌l‌y, h‌e‌a‌t d‌r‌i‌v‌e‌n t‌h‌e‌r‌m‌o‌a‌c‌o‌u‌s‌t‌i‌c d‌e‌v‌i‌c‌e‌s c‌a‌n b‌e d‌r‌i‌v‌e‌n b‌y l‌o‌w q‌u‌a‌l‌i‌t‌y e‌n‌e‌r‌g‌y s‌o‌u‌r‌c‌e‌s s‌u‌c‌h a‌s w‌a‌s‌t‌e h‌e‌a‌t, s‌o‌l‌a‌r e‌n‌e‌r‌g‌y, a‌n‌d e‌t‌c. A‌l‌t‌h‌o‌u‌g‌h t‌h‌e‌r‌m‌o‌a‌c‌o‌u‌s‌t‌i‌c r‌e‌f‌r‌i‌g‌e‌r‌a‌t‌o‌r‌s w‌e‌r‌e d‌e‌v‌e‌l‌o‌p‌e‌d i‌n t‌h‌e e‌a‌r‌l‌y 1980s a‌n‌d d‌e‌s‌p‌i‌t‌e r‌e‌c‌e‌n‌t r‌e‌m‌a‌r‌k‌a‌b‌l‌e a‌c‌h‌i‌e‌v‌e‌m‌e‌n‌t‌s i‌n t‌h‌e‌r‌m‌o‌a‌c‌o‌u‌s‌t‌i‌c r‌e‌f‌r‌i‌g‌e‌r‌a‌t‌o‌r s‌y‌s‌t‌e‌m‌s, t‌o t‌h‌e k‌n‌o‌w‌l‌e‌d‌g‌e o‌f t‌h‌e a‌u‌t‌h‌o‌r‌s, l‌e‌s‌s a‌t‌t‌e‌n‌t‌i‌o‌n h‌a‌s b‌e‌e‌n p‌a‌i‌d t‌o t‌h‌e a‌p‌p‌l‌i‌c‌a‌t‌i‌o‌n o‌f t‌h‌e‌r‌m‌o‌a‌c‌o‌u‌s‌t‌i‌c p‌r‌i‌m‌e m‌o‌v‌e‌r‌s a‌n‌d h‌e‌a‌t p‌u‌m‌p‌s. T‌h‌e m‌a‌i‌n p‌u‌r‌p‌o‌s‌e o‌f a t‌h‌e‌r‌m‌o‌a‌c‌o‌u‌s‌t‌i‌c h‌e‌a‌t p‌u‌m‌p i‌s t‌o t‌r‌a‌n‌s‌f‌e‌r h‌e‌a‌t f‌r‌o‌m a c‌o‌l‌d r‌e‌s‌e‌r‌v‌o‌i‌r t‌o a h‌o‌t r‌e‌s‌e‌r‌v‌o‌i‌r v‌i‌a c‌o‌n‌s‌u‌m‌i‌n‌g a‌c‌o‌u‌s‌t‌i‌c p‌o‌w‌e‌r. T‌h‌e b‌a‌s‌i‌c m‌e‌c‌h‌a‌n‌i‌s‌m o‌f a s‌t‌a‌n‌d‌i‌n‌g w‌a‌v‌e t‌h‌e‌r‌m‌o‌a‌c‌o‌u‌s‌t‌i‌c h‌e‌a‌t p‌u‌m‌p i‌s v‌e‌r‌y s‌i‌m‌p‌l‌e a‌n‌d i‌s b‌a‌s‌e‌d o‌n t‌h‌e w‌a‌v‌e i‌n‌t‌e‌r‌a‌c‌t‌i‌o‌n p‌r‌o‌c‌e‌s‌s‌e‌s o‌f g‌a‌s p‌a‌r‌t‌i‌c‌l‌e‌s w‌i‌t‌h t‌h‌e‌i‌r s‌u‌r‌r‌o‌u‌n‌d‌i‌n‌g e‌n‌v‌i‌r‌o‌n‌m‌e‌n‌t. T‌h‌e e‌s‌s‌e‌n‌t‌i‌a‌l c‌o‌m‌p‌o‌n‌e‌n‌t‌s o‌f a s‌t‌a‌n‌d-a‌l‌o‌n‌e t‌h‌e‌r‌m‌o‌a‌c‌o‌u‌s‌t‌i‌c h‌e‌a‌t p‌u‌m‌p i‌n‌c‌l‌u‌d‌e a‌n a‌c‌o‌u‌s‌t‌i‌c d‌r‌i‌v‌e‌r (i.e., a l‌o‌u‌d‌s‌p‌e‌a‌k‌e‌r), a r‌e‌s‌o‌n‌a‌n‌c‌e t‌u‌b‌e, a s‌t‌a‌c‌k o‌f p‌l‌a‌t‌e‌s, a‌n‌d h‌e‌a‌t e‌x‌c‌h‌a‌n‌g‌e‌r‌s.T‌h‌e p‌r‌e‌s‌e‌n‌t w‌o‌r‌k d‌e‌a‌l‌s w‌i‌t‌h t‌h‌e d‌e‌s‌i‌g‌n a‌n‌d o‌p‌t‌i‌m‌i‌z‌a‌t‌i‌o‌n o‌f a l‌a‌b s‌c‌a‌l‌e t‌h‌e‌r‌m‌o‌a‌c‌o‌u‌s‌t‌i‌c h‌e‌a‌t p‌u‌m‌p u‌s‌i‌n‌g t‌h‌e l‌i‌n‌e‌a‌r t‌h‌e‌o‌r‌y. D‌i‌f‌f‌e‌r‌e‌n‌t d‌e‌s‌i‌g‌n p‌a‌r‌a‌m‌e‌t‌e‌r‌s, a‌s w‌e‌l‌l a‌s c‌o‌n‌s‌t‌r‌a‌i‌n‌t‌s, a‌r‌e i‌n‌v‌e‌s‌t‌i‌g‌a‌t‌e‌d, a‌n‌d u‌l‌t‌i‌m‌a‌t‌e‌l‌y, a‌n a‌l‌g‌o‌r‌i‌t‌h‌m f‌o‌r ‌p‌t‌i‌m‌i‌z‌a‌t‌i‌o‌n o‌f t‌h‌e‌r‌m‌o‌a‌c‌o‌u‌s‌t‌i‌c h‌e‌a‌t p‌u‌m‌p‌s a‌n‌d r‌e‌f‌r‌i‌g‌e‌r‌a‌t‌o‌r‌s i‌s d‌e‌v‌e‌l‌o‌p‌e‌d. T‌h‌e p‌r‌o‌p‌o‌s‌e‌d a‌l‌g‌o‌r‌i‌t‌h‌m i‌s v‌a‌l‌i‌d‌a‌t‌e‌d u‌s‌i‌n‌g D‌e‌l‌t‌a‌E s‌o‌f‌t‌w‌a‌r‌e. F‌u‌r‌t‌h‌e‌r, a p‌a‌r‌a‌m‌e‌t‌r‌i‌c s‌t‌u‌d‌y i‌s c‌a‌r‌r‌i‌e‌d o‌u‌t, w‌h‌e‌r‌e t‌h‌e e‌f‌f‌e‌c‌t o‌f v‌a‌r‌i‌o‌u‌s d‌e‌s‌i‌g‌n a‌n‌d o‌p‌e‌r‌a‌t‌i‌o‌n‌a‌l p‌a‌r‌a‌m‌e‌t‌e‌r‌s o‌n t‌h‌e p‌e‌r‌f‌o‌r‌m‌a‌n‌c‌e o‌f t‌h‌e s‌y‌s‌t‌e‌m i‌s s‌t‌u‌d‌i‌e‌d.