Low Temperature Waste Heat Recovery Research Articles

Evaluation of structural phase transition by pyroelectric measurements

In non-centrosymmetric crystalline matter, marked by the pyroelectric effect, a change in temperature alters the materials spontaneous polarization, which further changes the charge density on the material's surface. This results in a current flow trough an external circuit, which differs drastically at the boundary between two crystallographic phases. Therefore, pyroelectric materials offer a great potential of low-temperature waste heat recovery by utilizing e.g. the Olsen-Cylce to convert residual heat into electric energy. A previous characterization is necessary to determine the operating conditions of the active material. This work presents a method to evaluate temperature depended pyroelectric properties, especially the pyroelectric coefficient p and the phase transition temperture TC, with the help of a computer controlled thermal/electrical stimulation and a simultaneously recording of the electrical response of the material. Here, the analysis with the Sharp-Garn-method [1] separates the pyroelectric from eventually disturbing non-pyroelectric signal, enabling the characterization of p and TC over a broad spectrum of materials, ranging from inorganic single crystals and ceramics to organic polymers.

Fluid selection of Organic Rankine Cycle for low-temperature waste heat recovery based on thermal optimization

The purpose of the present paper is to propose a methodology for the fluid selection of an Organic Rankine Cycle for low-temperature waste heat recovery. The selection of an optimal working fluid is carried out by an optimization process, using the Genetic Algorithm. Three decision variables are considered: the working fluid, the evaporation temperature and the condensation temperature. These variables are subjected to some constraints that take into account the good operation of the heat exchangers and the expander. The defect of efficiency and the total heat exchange area per unit of power output are selected as the objective functions to be minimized. The heat recovery is made possible by a hot water source, which assumes inlet temperatures of 100 °C and 150 °C. The water mass flow rate is fixed to 1.0 kg/s. The results show that fluids with low value of critical temperature, like Novec649, RE347mcc, R245fa, optimize the defect of efficiency, whilst, in order to minimize the total heat exchange area per unit of power output, fluids with high value of thermal conductivity and latent heat of vaporization must be selected. This work offers a tool to selected an optimal working fluid, among all possible candidates, for this type of applications.

The Experiment Research on Storage Characteristic of PCM Storage Device by Spheres Piled Encapsulated for Vehicle Waste Heat

For the thermal environment and the warming requirement of Vehicle, carry out experiment study on heat storage characteristic of phase change materials (PCM) encapsulated by Spherical stack. heat storage and release experiment process , changing factors such as medium flow rate and melting point which impact on PCM heat transfer characteristics , melting rate and response time have been analyzed. The results show that within the scope of experiment high medium flow rate is conducive to promote PCM melting rate and heat storage. In the experiments process, high melting point of PCM storage heat grade is high, but the low melting point of PCM is more suitable for vehicle motor, batteries in low temperature waste heat recovery. At the same time, multi-melting point PCM storage device with spheres piled encapsulated delamination mixed stowage was better satisfy the different condition of waste heat recovery and utilization than single melting point of PCM.

Thermodynamic analysis of a low-temperature waste heat recovery system based on the concept of solar chimney

The utilization of low-temperature waste heat draws more and more attention due to serious energy crisis nowadays. This paper proposes a low-temperature waste heat recovery system based on the concept of solar chimney. In the system, low-temperature waste heat is used to heat air to produce an air updraft in the chimney tower. The air updraft propels a turbine fixed at the base of the chimney tower to convert waste heat into electricity. The mathematical model of the system is established based on first law and second law of thermodynamics. Hot water is selected as the representative of low-temperature waste heat sources for researching. The heat source temperature, ambient air temperature and area of heat transfer are examined to evaluate their effects on the system performance such as velocity of updraft, mass flow rate of air, power output, conversion efficiency, and exergy efficiency. The velocity of air demonstrates a better stability than the mass flow rate of air and the pressure difference when temperature of heat source, ambient air temperature or area of heat transfer changes.

Design of a thermoacoustic heat engine for low temperature waste heat recovery in food manufacturing: A thermoacoustic device for heat recovery

There is currently an urgent demand to reuse waste heat from industrial processes with approaches that require minimal investment and low cost of ownership. Thermoacoustic heat engines (TAHEs) are a kind of prime mover that convert thermal energy to acoustic energy, consisting of two heat exchangers and a stack of parallel plates, all enclosed in a cylindrical casing. This simple design and the absence of any moving mechanical parts make such devices suitable for a variety of heat recovery applications in industry. In this present work the application of a standing-wave TAHE to utilise waste heat from baking ovens in biscuit manufacturing is investigated. An iterative design methodology is employed to determine the design parameter values of the device that not only maximise acoustic power output and ultimately overall efficiency, but also utilise as much of the high volume waste heat as possible. At the core of the methodology employed is DeltaEC, a simulation software which calculates performance of thermoacoustic equipment. Our investigation has shown that even at such a comparatively low temperature of 150 °C it is possible to recover waste heat to deliver an output of 1029.10 W of acoustic power with a thermal engine efficiency of 5.42%.

200℃以下のボイラー排ガスから低温廃熱回収が可能な高効率ふっ素樹脂熱交換器のご紹介

省エネ，省電力はあらゆる工場で取り組まれている重要課題である。従来より，そのまま捨てていた低温廃熱を有効利用したいと言う要望は有るが，低温領域での廃熱は酸露点腐食，汚れ付着による伝熱管性能低下等の課題により有効に回収することは困難とされていた。潤工社では，この課題をふっ素樹脂PFA伝熱管および構造の工夫により解決した。低温領域での廃熱回収を行うにあたり要求されるファクターとして，次の4点が挙げられる。（1）酸露点腐食に対する耐食性（2）ガス側圧力損失の低減（3）メンテナンス工数の削減（4）小型・軽量化弊社製品はガラスメーカーにて約14年間ほぼメンテナンスフリーにて使用された実績が有り，上記4点の優れた特徴を十分有している事が既に証明されている。また，直近では2つの製紙会社の異なるボイラー：廃棄物ボイラー（180t／h）及び黒液回収ボイラー（170t／h）にて実証試験を実施した。ともに伝熱管の腐食やスケールの付着，伝熱管の磨耗・劣化等が見られず良好な結果が得られた。潤工社製ふっ素樹脂熱交換器「フロロエックス®グリッドシリーズ」は排ガス中の腐食成分に対して卓越した耐食性と非粘着性を発揮するとともに，総括伝熱係数も40～50kcal／m2・℃・hrと大きく，他材質の低温領域用廃熱回収装置との比較においても充分なメリットを有していると判断できる。

Performance Assessment of Low-Temperature Thermal Storage with Electromagnetic Control

This study presents electromagnetic-controlled thermal storage (ECTS) that can be directly implemented in strategies of low-temperature waste heat recovery for energy-consuming equipment. A magnetic nanofluid (MNF) prepared from fine iron ferrite ferromagnetic particles is recommended as a latent heat medium (LHM). During electromagnetic induction, local flow fluctuations are generated and thermal convection in the MNF can be enhanced. The achieved results demonstrated that ECTS has a wide operational range and an optimum storage efficiency of 84.46%. Thus, a self-perturbation mode used to enhance thermal energy transportation can be designed for numerous waste heat management applications.

Study on Marine Diesel Engine Waste Heat Recovery System with Multi-Stage Flash

As international oil price rise rapidly, the proportion of the fuel cost share of the transport cost has become increasingly high. At the same time, in order to reduce CO2 emission, the meeting of MPEC formulated and adopted the resolution on EEDI, so saving energy and reducing emission has become a marine industry benchmark. In this paper, through the study on marine diesel engine waste heat recovery system with multi-stage flash, establishing the universal model of multi-stage flash unit, and optimizing the parameters of the low-temperature waste heat recovery system with multi-stage flash. This paper constructs the power equation in matrix model, and each matrix of the model has a simple rule to be filled in, which make it versatile, and suitable for computerization, through estimating the power generation and CO2 emission reduction of the system on main diesel engine different loads, analyzing the waste heat recovery system with economic method finally.

Economic Analysis of the Absorption Heat Pump in Supercritical Unit

As an effective energy-saving device, the heat pump is environmentally friendly and advantageous in the recovery of low-temperature and middle-temperature waste heat. So it is increasingly being used in practical applications. The circulating water which is produced by power plants has a large number of low-temperature waste heat. It will bring huge economic and environmental benefits by using heat pump technology to recover those waste heat energy. The application of the heat pump in supercritical unit is discussed as the example of central heating project using waste heat in a power plant. And the basic principle of absorption heat pump is introduced. The economy, energy conservation and environmental benefits of lithium bromide absorption heat pump are also analyzed when it is used in 600MW supercritical unit.

Selection of Working Fluids for Low-Temperature Waste Heat Recovery Using Organic Rankine Cycle

As for the industrial exhaust heat with the temperature ranging from 120°C to 200°C, 5 working fluids commonly used in organic Rankine cycle, namely R113、R123、R134a、R245fa and R600a, have been analysed from the perspective of safety, environment and economical efficiency. The results show that: R123 is of great poison, but its thermal economical efficiency is the best, especially under the condition of high temperature. The suitable ambient temperature ranges from 20-35°C. R245fa belongs to a safe and environment friendly fluid. For its best comprehensive property and wide range of ambient temperature, R245fa is very beneficial to the ORC system.

Performance analysis of double organic Rankine cycle for discontinuous low temperature waste heat recovery

This research proposes a double organic Rankine cycle for discontinuous waste heat recovery. The optimal operation conditions of several working fluids have been calculated by a procedure employing MATLAB and REFPROP. The influence of outlet temperature of heat source on the net power output, thermal efficiency, power consumption, mass flow rate, expander outlet temperature, cycle irreversibility and exergy efficiency at a given pinch point temperature difference (PPTD) has been analyzed. Pinch point analysis has also been employed to obtain a thermodynamic understanding of the ORC performance. Of all the working fluids investigated, some performances between each working fluid are rather similar. For a fixed low temperature heat source, the optimal operation condition should be mainly determined by the heat carrier of the heat source, and working fluids have limited influence. Lower outlet temperature of heat source does not always mean more efficient energy use. Acetone exhibits the least exergy destruction, while R245fa possesses the maximal exergy efficiency at a fixed PPTD. Wet fluids exhibit lower thermal efficiency than the others with the increasing of PPTD at a fixed outlet temperature of heat source. Dry and isentropic fluids offer attractive performance.

Implementation and evaluation of a low temperature waste heat recovery power cycle using NH3 in an Organic Rankine Cycle

With increasing cost for power generation opportunities for small scale power generation from waste heat have increased. The awareness of untapped resources such as local waste heat streams as well as the available range of technology and products to harvest such streams is increasing steadily though field data is scarce for applications below 100 °C entry temperature. ORC applications have a large number of open parameters and therefore require field data for correlation of models.This paper presents field data and analysis of an ORC power generation plant operating with NH3. The unit operates on waste heat from a Swedish pulp mill at an available temperature of 75 to 85 °C. Performance at varying heat source conditions and capacity is reported as well as an analysis of the particular investment case.The data was generated during a 15 day period and show a thermal efficiency of 8–9% at capacities from 50 to 100%. The results indicate a flat thermal efficiency from 20 to 100% capacity.Investment case analysis is based on a purchase model while the chosen economic model is a supplier own-and-operate arrangement supplying the mill with power at a predefined cost during an extended period of time.

Two Algorithms for the Reliable Estimation of Organic Rankine Cycle Performance

As the demand grows for low-temperature waste heat recovery systems, organic Rankine cycles (ORCs), and other alternatives to traditional steam, Rankine cycles are becoming more common in industry. Although analytical tools exist that can predict the performance of a steam cycle in a given waste-heat application, the development of a similar tool for ORCs has been hampered by the large choice of possible working fluids. In this paper, two methods are presented with the aim of providing an estimate of the best performance possible for any ORC in a given industrial application. The first is a purely analytical approach assuming an idealized fluid, and the second compares real fluids through cycle simulations to select the most appropriate parameters for the application. The analytical approach provides a rough baseline for performance, while the simulation method refines the estimate to give predictions that are more consistent with the documented performance of ORC plants currently in operation. Together, the two approaches represent a robust means of quickly estimating the capability of an ORC plant and to allow quick comparisons with other technologies.

Modeling, experimental study and optimization on low-temperature waste heat thermoelectric generator system

Thermoelectric generation technology, due to its several kinds of merits, especially its promising applications to waste heat recovery, is becoming a noticeable research direction. Based on basic principles of thermoelectric generation technology and finite time thermodynamics, thermoelectric generator system model has been established. In order to investigate viability and further performance of the thermoelectric generator for waste heat recovery in industry area, a low-temperature waste heat thermoelectric generator setup has been constructed. Through the comparison of results between theoretic analysis and experiment, reasonability of this system model has been verified. Testing results and discussion show the promising potential of using thermoelectric generator for low-temperature waste heat recovery, especially in industrial fields. Several suggestions for system performance improvement have been proposed through the analysis on this system model, which guide optimization and modification of this experimental setup. By integrating theoretic analysis and experiment, it is found that besides increasing waste heat temperature and TE modules in series, expanding heat sink surface area in a proper range and enhancing cold-side heat transfer capacity in a proper range can also be employed to enhance performance of this setup.

G124 低温排熱回収用ポンプレスランキン型サイクルの実験検証(OS-8:温度差発電(I))

G124 低温排熱回収用ポンプレスランキン型サイクルの実験検証(OS-8:温度差発電(I))

Characteristics of Small ORC System for Low Temperature Waste Heat Recovery

This paper describes fundamental characteristics of a small organic Rankine cycle (ORC) system to be used for power generation from low temperature heat sources such as waste heat and solar energy. The aim of the study was to develop an ORC system with a small power output of less than 1 kW with a hot source with temperature ranging from 60 to 100°C and a cold source with temperature ranging from 10 to 30°C. An ORC system with a potential to produce a turbine/expander power of 250 W was built and its fundamental characteristics were elucidated. A turbine/expander was not actually installed but was simulated by controlling two expansion valves. First, steady-state energy balance of the system was examined and the required turbine/expander efficiency was estimated in consideration of pump power of the working fluid. Then, the relationship between the expansion ratio and thermal efficiency was elucidated. The most important result of the study was that for maintaining high thermal efficiency in the case that the temperature difference between hot and cold sources varies during operation, it is indispensable to employ a variable expansion mechanism by which the expansion ratio of the turbine/expander can be adjusted to fit the optimal ratio at the operating temperature level.

Experimental study on low-temperature waste heat thermoelectric generator

In order to further studies on thermoelectric generation, an experimental thermoelectric generator unit incorporating the commercially available thermoelectric modules with the parallel-plate heat exchanger has been constructed. The experiments are carried out to examine the influences of the main operating conditions, the hot and cold fluid inlet temperatures, flow rates and the load resistance, on the power output and conversion efficiency. The two operation parameters such as the hot fluid inlet temperature and flow rate are found to significantly affect the maximum power output and conversion efficiency. A comparison of the experimental results with those from the previously published numerical model is also presented. The meaningful results obtained here may serve as a good guide for further improving the numerical model and conducting a system level optimization study in the next step. Also, the present study shows the promising potential of using this kind of thermoelectric generator for low-temperature waste heat recovery.

Study on an activated carbon fiber–ethanol adsorption chiller: Part II – performance evaluation

This article presents the performance evaluation of a two-bed, activated carbon fiber (ACF)–ethanol adsorption chiller, which has been studied on the basis of the transient modelling developed by the same authors [B.B. Saha, I.I. El-Sharkawy, A. Chakraborty, S. Koyama, Study on an activated carbon fiber–ethanol adsorption chiller: Part I – system description and modelling, International Journal of Refrigeration, submitted for publication]. This innovative adsorption chiller, where pitch based ACF of type A-20 is taken as the adsorbent utilizes effectively the low-temperature waste heat sources of temperature between 60 and 95 °C along with a cooling source at ambient temperature. We have found that, regardless of the initial mass distribution, the ACF–ethanol adsorption chiller is able to achieve the same cyclic-steady-state within three half cycles or 1890 s. Simulation results show that the optimum COP values are obtained at driving source temperatures between 80 and 85 °C and makes this chiller suitable for low-temperature waste heat recovery with relatively higher performance.

A121 近接場光を用いたナノギャップ熱光起電力発電(マイクロ・ナノスケール2)

It is predicted that the energy consumption will increase. But, the main energy, oil, will be depleted in the near future. So, the energy recycle system is important. The TPV(Thermo Photo Voltaic) system is one of the energy recycle systems. The TPV system mainly converts the near infrared rays to electrical energy. If the evanescent wave can be applied to TPV system, the energy recycle system which is much effective in the low temperature waste heat recovery will be possible. So, in this paper, We tried to investigate an effect of near-field radiation (evanescent wave) to enhancement of thermophotovoltaic (TPV) generation of electricity.

High performance functionally graded and segmented Bi2Te3-based materials for thermoelectric power generation

Bi2Te3-based materials possess a figure of merit maximum over a narrow temperature range. When used in a generating mode over a large temperature difference the material operates at a substantially lower overall figure of merit than its maximum value. The conversion efficiency of a thermoelectric generator for low temperature waste heat recovery can be increased by employing functionally graded or segmented materials. In this work functionally graded p-type Bi2Te3-based thermoelectric materials have been prepared from melt by the Bridgman method using double doping technique. Segmented n-type thermoelement has been fabricated by joining two Bi2Te3-based materials with figure of merit maximum at 270 K and 380 K. The thermoelectric properties of the materials and a thermocouple comprised of p-type functionally graded and n-type segmented materials have been measured over a temperature range 200 K–450 K. The material efficiency of the thermocouple over the temperature gradient 223 K–423 K is estimated to be 10% compared with 8.8% for a standard Bi2Te3-based materials.