Low Temperature Waste Heat Recovery Research Articles

Thermal performance analysis of ground source heat pump system for low-temperature waste heat recovery storage

This study investigated the thermal performance of a ground source heat pump (GSHP) system for low-temperature waste heat storage. Considering the large amount of low-temperature heat from industrial effluents wasted to the environment, this study intends to store this low-temperature waste heat in the ground. A GSHP system for low-temperature waste heat storage was established, which could simultaneously achieve heat storage and extraction. In this system, the borehole cluster comprises two parts: inner and outer layers of ground heat exchangers (GHEs). The inner layer was used for space heating as a common GHE, which extracts heat from the ground, whereas the outer layer connected to the industry was designed for injecting low-temperature waste heat to the ground seasonally. The heat fluxes of the GHEs for heat injection and extraction were set differently and were taken as two different strengths of heat sources in this study. A heat and moisture transfer model was established and experimentally validated. Subsequently, the waste heat storage and heat extraction processes are modelled numerically. The results show that the average soil temperature increases by at least 2.63 and 6% when the heat flux of the outer layer GHEs are 40 and 50 Km−1, respectively. It reveals that the injection of low temperature waste heat into the soil is not only beneficial to waste heat recovery, but can also alleviate soil thermal imbalance, providing significant support in heating dominated area, especially in cold regions. This study complements the thermal analysis between two different strength of heat sources, providing a reference for practical engineering design.

Synthesis of waste heat recovery using solar organic Rankine cycle in the separation of benzene/toluene/p-xylene process

Current energy intensification measures of dividing wall columns are mainly based on vapor recompression and organic Rankine cycle technologies. Vapor recompression can achieve self-heat recovery of the dividing wall column to use a large part of the waste heat. And the organic Rankine cycle recovers the surplus low-temperature waste heat. However, the efficiency of such low-temperature waste heat recovery by organic Rankine cycle is always low. Additionally, the current design of such energy systems is based on conventional fossil fuels, which are not conducive to long-term development. This paper proposes using solar energy to improve the efficiency of low-temperature waste heat recovery. Based on this concept, a novel waste heat recovery combined solar organic Rankine cycle is established, which is integrated into a vapor recompression assisted dividing wall column system to simultaneously recover waste heat and produce electric power. In addition, the organic Rankine cycle and solar organic Rankine cycle assisted systems were compared. Furthermore, a robust solar-energy design and optimization procedure was used to optimize the three proposed schemes by considering the actual solar fluctuations in Islamabad. Performance analysis and techno-economic evaluation were executed under nominal and actual conditions. The results show that solar radiation can increase the waste heat recovery efficiency and reduce the actual total annual cost.

A Literature Review of the Kalina Cycle and Trends

The demand for electricity and power has been increasing with the increase of the population of the world. The Covid-19 Pandemic has affected the way of life of human beings starting last year. The pandemic and economic downturn also affected the electricity demand of the world, but this is only short-term. Once the lockdowns around the world ease and back to normal situation begin, demand for power and electricity shall continue to grow. The century-old Rankine cycle has been the basis for power plants widely used today. However, a modified Rankine cycle known as the Kalina cycle has been proving more efficient than the standard Rankine cycle and might be able to provide the additional power needed in medium and low-temperature sources and waste heat recovery. This paper look into the development of the Kalina cycle and the trends that might be of use for the global electricity requirement.

Comparing district heating options under uncertainty using stochastic ordering

District heating is expected to play an important role in the decarbonisation of the energy sector in the coming years since low carbon sources such as waste heat and biomass are increasingly being used to generate heat. The design of district heating often has competing objectives: the need for inexpensive energy and meeting low carbon targets. In addition, the planning of district heating schemes is subject to multiple sources of uncertainty, such as variability in heat demand and energy prices. This paper proposes a decision support tool to analyse and compare system designs for district heating under uncertainty using stochastic ordering (dominance) so that decision-makers can make robust decisions. The uncertainty in input parameters of the energy system model together with general scenarios are introduced to generate distributions of net present costs and emissions for each design. To perform inference about the induced distributions of outputs, we apply the orderings in the mean and dispersion. The proposed approach is demonstrated in an application to the waste heat recovery problem in district heating in Brunswick, Germany. The results obtained show that heat pump, a low carbon design option, is more robust in comparison to combined heat and power (CHP) and a mix of CHP and heat pump under all three scenarios, highlighting that robustness is an attractive feature of low-temperature waste heat recovery. • Decisions regarding energy planning involve uncertainty. • New low-carbon technologies are being introduced as part of district heating. • Stochastic ordering is proposed to compare the system designs’ performance under uncertainty. • The orderings in mean and dispersion are considered for waste heat recovery.

Experimental investigation on cooling cogeneration plant for low temperature waste heat recovery process

Experimental investigation on cooling cogeneration plant for low temperature waste heat recovery process

Integracija toplotnih pumpi u postojeći energetski sistem u malim i srednjim preduzećima

Industry processes are characterized by large amounts of energy losses dissipated as waste heat to the ambient. In industry sectors analysed in the US, China and EU28 lowtemperature waste heat below 230ºC makes up from 33% up to 60% of waste heat. The recovery of low-temperature waste heat is usually complex, affected by the user demand, mismatches between the waste heat source and the user demand, limited space for heat recovery facilities, the heat-power conversion is not efficient for low-temperature waste heat, payback period, etc. The purpose of this paper is to present a methodology for technical and economic analysis of waste heat recovery. To address the issue of sensible criterion, methodology appropriate for small and medium enterprises is developed and in this paper, the user-friendly optimization integrating the heat exchange, energy conversion and heat storage is presented. A case study of waste heat recovery from an induction machine cooling system is used to demonstrate the applicability of the proposed methodology. The introduced methodology can simplify the heat pump integration process, and the proposed method can be further extended to other industrial processes for low-grade waste heat recovery.

Thermal Performance Analysis of Ground Source Heat Pump System for Low-Temperature Waste Heat Recovery Storage

Thermal Performance Analysis of Ground Source Heat Pump System for Low-Temperature Waste Heat Recovery Storage

Thermal-Economic Optimization and Working Fluid Selection of Subcritical Organic Rankine System for Low-Temperature Waste Heat Recovery

Thermal-Economic Optimization and Working Fluid Selection of Subcritical Organic Rankine System for Low-Temperature Waste Heat Recovery

A Latent Heat Storage System for Low-Temperature Applications: From Materials Selection to Prototype Performances

The industrial sector is increasingly obliged to reduce its energy consumption and greenhouse gases emissions to contribute to the world organizations’ targets in energy transition. An energy efficiency solution lies in the development of thermal energy storage systems, which are notably lacking in the low-temperature range (50–85 °C), for applications such as district heating or low-temperature waste heat recovery. This work aims to bring a latent heat storage solution from material selection to prototype evaluation. The first part of this paper is dedicated to the characterization and aging of a phase change material selected from a screening of the literature (fatty acid mixture mainly composed by stearic and palmitic acid). Then, this material is encapsulated and tested in a prototype whose performances are evaluated under various operating conditions. Finally, a numerical model validated by the experimental results is used to explore the influence of a wider range of operating conditions, dimensioning choices, and material conductivity improvements.

Comparative analysis of battery electric vehicle thermal management systems under long-range drive cycles

Due to increasing regulation on emissions and shifting consumer preferences, the wide adoption of battery electric vehicles (BEV) hinges on research and development of technologies that can extend system range. This can be accomplished either by increasing the battery size or via more efficient operation of the electrical and thermal systems. This study endeavours to accomplish the latter through comparative investigation of BEV integrated thermal management system (ITMS) performance across a range of ambient conditions (-20 °C to 40 °C), cabin setpoints (18 °C to 24 °C), and six different ITMS architectures. A dynamic ITMS modelling framework for a long-range electric vehicle is established with comprehensive sub models for the operation of the drive train, power electronics, battery, vapor compression cycle components, and cabin conditioning in a comprehensive transient thermal system modelling environment. A baseline thermal management system is studied using this modelling framework, as well as four common thermal management systems found in literature. This study is novel for its combination of comprehensive BEV characterization, broad parametric analysis, and the long range BEV that is studied. Additionally, a novel low-temperature waste heat recovery (LT WHR) system is proposed and has shown achieve up to a 15% range increase at low temperatures compared to the baseline system, through the reduction of the necessary cabin ventilation loading. While this system shows performance improvements, the regular WHR system offers the greatest benefit, a 13.5% increase in cold climate range, for long-range BEV drive cycles in terms of system range and transient response without the need for additional thermal system equipment.

The Thermal Economy of a Circulating Medium and Low Temperature Waste Heat Recovery System of Industrial Flue Gas

The waste heat recovered by traditional industrial waste heat recovery systems is mostly high-temperature flue gas and combustible gas, while the waste heat of medium and low temperature flue gas that accounts for more than 50% of the total waste heat resources has been ignored, which is not conducive to the effective energy saving of industrial production and manufacturing process. In the meantime, few studies have concerned about the changes in the economy of circulating industrial waste heat recovery system. Therefore, to fill in this research gap, this paper aimed at the economy problem of circulating medium and low temperature industrial waste heat recovery system and carried out a series of research. The paper completed the thermodynamic analysis of different medium and low temperature waste heat recovery modes of industrial flue gas, and gave the analysis steps of the economy of circulating medium and low temperature waste heat recovery system of industrial flue gas. The effectiveness and accuracy of the thermodynamic and thermo-economic models constructed in the paper were proved by experimental results.

Power generation of thermoelectric generator with plate fins for recovering low-temperature waste heat

Low-temperature waste heat has great potential for renewable power because it accounts for around 60% of total industrial waste heat. This study develops a model of integrating thermoelectric generation, computational fluid dynamics, and plate fins to figure out a low-temperature waste heat recovery system for power generation. The effect of the number of partitions of a thermoelectric module on its performance is examined, and the results show that a single module without a partition can provide accurate predictions. Four different combinations between wastewater and air in the hot and cold channels under three different Reynolds numbers (i.e., Re = 10, 100, and 1,000) on thermoelectric modules’ performance suggest that only combining hot wastewater and cooling water can contribute electricity to a certain extent. By installing fins with a number range of 0–27, it indicates that fin installation can dramatically intensify heat transfer and thermoelectric modules’ performance. The optimal number of fins at Re = 10 and 100 is 21, whereas it is 27 at Re = 1,000. The maximum total output power and mean conversion efficiency are 0.411 W and 0.95%, respectively, with 27 fins at Re = 1,000. These values account for 105.5% and 43.94% improvements when compared to the TEMs without fins. Even though installing fins increases the pressure drop in the channel, its value is much smaller than the generated power (less than1%). The developed method in this study can be used to efficiently and accurately predict the performance of thermoelectric modules, and obtained results have provided practical insights into the design of low-temperature waste heat recovery systems for green power generation.

Performance Analysis of the Technology of High-Temperature Boiler Feed Water to Recover the Waste Heat of Mid-Low-Temperature Flue Gas.

In coal-fired power plants, most of the working fluids used in a mid–low-temperature flue gas waste heat recovery system (FGWHRS) are low-temperature boiler supply air or condensate water in the flue gas condenser. This is prone to cause low-temperature corrosion, as the system temperature is lower than the acid dew point of the flue gas. In this study, an experimental apparatus was set up at the entrance of the desulfurization tower of a 330 MW unit in Xinjiang, China, which uses the technology of high-temperature boiler feed water (above 80 °C) to recover the waste heat of mid–low-temperature flue gas. The heat exchange performance of the mid–low-temperature FGWHRS was evaluated under different working conditions, and the optimal input parameters of the system for each considered working condition are given based on the analysis. It was found that the low-temperature corrosion in the system could be avoided using this technology. To eliminate low-temperature corrosion, the lowest temperature for the inlet water was predicted to be 69 °C in our study via curve fitting based on the experimental data. The results could provide a theoretical basis and engineering guidance for determining the best heat recovery strategy of mid–low-temperature FGWHRS.

Performance comparison of different heat pumps in low-temperature waste heat recovery

The recovery of low-temperature waste heat can greatly reduce the fossil energy consumption, among whose technologies heat pumps show excellent energy saving effect and environmental friendliness. There are four commercial types of heat pumps, the absorption heat pump (AHP), absorption heat transformer (AHT), steam jet pump (SJP) and mechanical heat pump (MHP). To compare the energy performance of the four types of heat pumps in low-temperature waste heat recovery (WHR), simulation models for these heat pumps are established by Aspen Plus. The heat demand of the user side is described by a heat ratio (the ratio of the user side heat demand to the waste heat). The energy performance of four kinds of heat pumps in low-temperature WHR is compared and analyzed by the coefficient of performance (COP), exergy efficiency and annual savings of standard coal. The results show that when the heat ratio is higher than about 0.5, the MHP has the best energy performance. When the heat ratio is lower than about 0.5, the AHT is the best, for it can not only meet the heat demand of the user side, but make full use of the waste heat source as well. The performance of SJP is always better than that of AHP. Combined with qualitative economic analysis, it is recommended that the SJP is a good choice when HR is higher than about 0.7, otherwise the AHT is a suitable choice. This study can provide references for choosing a suitable heat pump in the low-temperature WHR.

Technology to Reduce GHG from Ships - Low Temperature Waste Heat Recovery System for Gas Fuelled Ships

Technology to Reduce GHG from Ships - Low Temperature Waste Heat Recovery System for Gas Fuelled Ships

Ten megawatt scale vapor compression heat pump for low temperature waste heat recovery: Onsite application research

In order to limit global warming of 1.5 °C before 2050, the heat pump with waste heat recovery has been acknowledged as an effective technical solution. In this paper, a new kind of centrifugal heat pump system is applied to recover the waste heat from a steel plant for district heating. Two centrifugal compressors with vapor injection and two-cycle parallel connected system configuration are adopted to achieve higher energy efficiency and larger heating capacity. From simulation, the COP is expected to be more than 6 with a temperature rise of above 30 °C. To validate the calculation results, a 10 MW scale (9.5 MW) centrifugal heat pump was installed and tested in Angang Lingshan steel plant of China. With the waste water inlet temperature of 32.5 °C and hot water outlet temperature of 62.5 °C, the tested COP and heating capacity were 6.67 and 9.67 MW, respectively. The heating capacity of the system was greater than the heating load under severe conditions. Environmental and economic analyses of the waste heat recovery system are presented, showing advantages compared to the conventional heating methods. The PER of megawatt compression heat pump is as high as 2.53 and the payback period of this waste heat recovery system is 1.66 years.

Performance Analysis of a Printed Circuit Heat Exchanger with a Novel Mirror-Symmetric Channel Design

The printed circuit heat exchanger (PCHE) is a promising waste heat recovery technology to improve energy efficiency. The current investigation presents the experimental results on the thermal performance of a novel PCHE for low-temperature waste heat recovery. The novel PCHE was manufactured using precision machining and diffusion bonding. The thermal performances, such as effectiveness and NTU values at different temperatures, are evaluated, and water is used as a working fluid. The experimental results indicate that the PCHE’s effectiveness is around 0.979 for an inlet flow temperature of 95 °C. The predominant factors affecting the thermal performance of the PCHE are the inlet flow temperature and the flow rate of the working fluid. In addition, a comparison of the experimental results and the literature shows that the effectiveness of the PCHE is better than the others, which have fewer layers of PCHE fins.

Design analysis of the “Schwartz D” based heat exchanger: A numerical study

Triply Periodic Minimal Surfaces (TPMS) have promising thermophysical properties, which makes them a suitable candidate in the production of low-temperature waste heat recovery systems. A TPMS thermal performance is connected to the complex flow patterns inside the pores and their interactions with the walls. Unfortunately, the experimental study’s design analysis and optimization of TPMS heat exchangers are complicated due to the flow pattern complexity and visual limitations inside the TPMS. In this study, three-dimensional steady-state, conjugate heat transfer (CHT) simulations for laminar incompressible flow were carried out to quantify the performance of a TPMS based heat exchanger. TPMS Lattices based on Schwartz D architecture was modeled to elucidate the design parameters and establishing relationships between gas velocity, heat transfer, and thermal performance of TPMS at different wall thicknesses. In this study, four types of lattices from the same architectures with varying wall thickness were examined for a range of the gas velocity, with one design found to be the optimized lattice providing the highest thermal performance. The results and methodology presented here can facilitate improvements in TPMS-heat exchangers’ fabrication for recycling the waste heat in low pitch thermal systems.

Conversion of steam power plant into cogeneration unit - Case study

One of possible solutions leading to the increase of steam power plant thermal efficiency is its conversion into a cogeneration unit. However, it requires the heat recipient to be on-site and, if so, it may be done by implementation of absorption heat pump (AHP) technology with low temperature waste heat recovery and utilization. The paper presents results of an analysis of benefits resulting from implementation of absorption heat pump into the steam power plant for recovery of low temperature waste heat, due to additional demand for heat delivery to dedicated recipient (DHR). The demand for heat along the whole year was assumed and the calculations were performed for two cases. In the first case, which was called the reference case, the heat was produced by dedicated heat exchanger (DHX) fed with steam taken from the pipeline between the medium and low-pressure turbine sections (MPLPP). In the second case, absorption heat pump (AHP) as the main unit for heat production and recovery was assumed. However, due to insufficient heat production in some conditions, peak heat exchanger (PHX) placed directly behind the heat pump was considered. Both heat pump and pick heat exchanger were fed with steam taken from MPLPP, however, due to the AHP requirements the stem was mixed with hot water taken from hot water tank to achieve the steam saturation state. Results of calculations performed show that implementation of a heat recuperation by absorption heat pump implemented to conventional steam power plant increases the overall efficiency of cogeneration system, but at the same time it causes the electricity production to decrease. Moreover, the production of heat by absorption heat pump has lower impact on the electricity generation compared to generation of heat by conventional heat exchanger. If reference power plant without heat production is considered, due to the heat pump implementation the electricity production decreases of about 1.32% for heat production with dedicated heat exchanger, and of about 0.89% for absorption heat pump with peek heat exchanger respectively. It means that, owing to implementation of AHP instead of DHX with the same heat production, the power plant may generate more than 0.4% of total electricity produced.

Design of a Database of Case Studies and Technologies to Increase the Diffusion of Low-Temperature Waste Heat Recovery in the Industrial Sector

The recovery of waste heat is a fundamental means of achieving the ambitious medium- and long-term targets set by European and international directives. Despite the large availability of waste heat, especially at low temperatures (<250 °C), the implementation rate of heat recovery interventions is still low, mainly due to non-technical barriers. To overcome this limitation, this work aims to develop two distinct databases containing waste heat recovery case studies and technologies as a novel tool to enhance knowledge transfer in the industrial sector. Through an in-depth analysis of the scientific literature, the two databases’ structures were developed, defining fields and information to collect, and then a preliminary population was performed. Both databases were validated by interacting with companies which operate in the heat recovery technology market and which are possible users of the tools. Those proposed are the first example in the literature of databases completely focused on low-temperature waste heat recovery in the industrial sector and able to provide detailed information on heat exchange and the technologies used. The tools proposed are two key elements in supporting companies in all the phases of a heat recovery intervention: from identifying waste heat to choosing the best technology to be adopted.