Papers by Keyword: Waste Heat

Abstract: Waste heat utilization is a critical aspect of enhancing energy efficiency and sustainability in various systems. This study investigates the recovery of waste heat using a heat exchanger installed at the outlet of a small-sized engine, demonstrating significant temperature control capabilities. The introduction of hot air from the heat exchanger effectively increased the ambient room temperature from 20 °C to 48 °C within 90 minutes. The heat exchanger's effectiveness improved with higher initial exhaust gas temperatures, as demonstrated across three test cases. In Case I, the room temperature rose to 33 °C with an initial exhaust temperature of 61 °C. Cases II and III showed further increases to 43 °C and 45.7 °C, respectively, corresponding to higher exhaust temperatures of 77 °C and 84 °C. A notable achievement was the consistent improvement in heat exchanger performance, evidenced by increased outlet temperatures and decreased exhaust temperatures, indicating efficient heat transfer. The effectiveness of the device improved from 0.31 to 0.55, highlighting its potential for energy-efficient ambient temperature regulation. However, the study also identified certain limitations. The temperature rise plateaued after 90 minutes, suggesting a limit to the heat exchanger’s capacity due to its size. Additionally, the minimal temperature difference between 60 and 90 minutes in Case III indicated that the engine had reached its peak efficiency, thereby limiting further heat recovery.

Abstract: Extrusion is a fundamental procedure of polymer processing and is used to produce tubular profiles, foils, cable coatings, etc. Rising energy prices increase the pressure for extruder manufacturers and operators to cut costs. Nowadays, extruder manufacturers are forced to develop more energy-efficient extruders. One possibility to reach that goal is to reuse the occurring waste heat during the extrusion process. Operators could use the waste heat within their own company to reduce their primary energy costs. The prediction of energy consumption and usage of waste heat for new extrusion lines as well as existing extrusion lines with new products within the planning stage is very important. Additionally the energy recovery for new extrusion lines has to be projected within planning stage. The research approach is to enable the construction of energy recovery for future production based on theoretical view and the energy monitoring of real extrusion lines. Therefor a program was developed to forecast the amount of waste heat. The energy monitoring included the energy consumption of the main consumers and the waste heat amount of cooling chambers and barrel cooling for three different single grooved barrel extruders. The energy monitoring results show that some of the temperature of the cooling chambers qualifies for reutilization. The barrel cooling waste heat can be fully reused. The program calculates the cooling of the tubular profile with finite element difference wherein the heat transfer is calculated in the radial direction. The thermal state of the tubular profile can be simulated at every position within the extrusion line. Furthermore the thermal output into the coolant can be calculated. The calculated and collected data are satisfactory more often than not. Based on the energy monitoring results concepts for the usage of waste heat were elaborated. Thereupon measures for the usage of waste heat were implemented and validated.

Abstract: The paper presents the preliminary design of the special heat exchanger. The device under consideration is the kind of immersed coil heat exchangers. It consists of three vertical coils: two coils are standard, water is used as a heating medium; one coil is filled by the refrigerant R134a which transfers the waste heat from refrigeration and air conditioning system during the boiling processes. In order to prevent the possible refrigerant leakage, the special buffer layer filled with the nanofluid is mounted in the Freon coil. Thermophysical properties of the nanofluid cause the intensification of the heat transfer through the buffer layer and the same increase of the heat transfer rate. Calculations of thermal power were made. Correlations of heat transfer coefficients in curved tubes, pressure drop correlations for flow through helical coil tubes and correlations describing the heat transfer in the buffer layer, were applied. Results of the calculations indicate of the influence of of Freon coil on the exchanger heat transfer rate. Heat power of Freon coil is about 7 – 25% of water coil thermal power. Thus, the waste heat applied significantly increases the exchanger heat transfer rate.

Abstract: In the paper the author presents the possibilities of the application of the electrolytic technique for the investigation of heat transfer coefficients in channels with nanofluids. The electrolytic technique called the limiting current method enables to obtain mass transfer coefficients on the basis of the electrochemical processes and the laws governing these physical phenomena. The exemplary graph presenting the limiting currents values resulting from the experiment is shown in Fig. 1. These are the voltammograms at different Reynolds numbers and the ion concentration C_b. Heat transfer coefficients can be calculated using the correlations describing the analogy of mass and heat transfer processes. Some cases of the possible application of the electrolytic technique and factors influencing the mass transfer experiment including the state of the electroactive surface, change in ion concentration and thickness of the diffusion layer are discussed in [1]. In this work the author focused on the mass transfer experiment with the application of the nanofluid. Special properties of the nanofluid should be taken into account in the investigations. The paper presents the preliminary results of the experiment with nanofluid in the annular channel.

Abstract: This work explores the utilization of alternative refrigerants to the conventional silica gel + water adsorption pair for the adsorption chiller cycle. Water as the working fluid in the cycle limits the cooling temperatures to above 0°C due to its triple point. The activated carbon Maxsorb III is thus considered as the adsorbent due to its high micro-porous characteristics which lead to higher uptake values. The isotherms of this adsorbent with natural refrigerant Propane, n-butane as well as refrigerants HFC-134a, R507a and R-32 are fitted to the Dubinin-Astakhov equation and the parameters tabulated. With these isotherms, the performances of these pairs with respect to their Specific Cooling Effects (SCE) are compared for assorted cooling temperature, ambient temperature and waste temperature requirements. It was found that the natural refrigerant propane exhibits the most favorable operational conditions when the required cooling temperature is below 0°C. A mathematical model is thus developed to predict the cycle of the propane cycle and is found to show a good fit to the experimental results.

Abstract: This research presents a passive method of waste heat recovery and conversion to electricity using Thermo-Electric Generator (TEG). For this purpose, a lab scale bench-top prototype of waste heat recovery and conversion system was designed and fabricated. This bench top system consists of the thermoelectric generators (TEGs) sandwiched between two heat pipes, one connected to the hot side of the TEG and the second connected to the cold side of the TEG. A 2 kW electric heater was used to replicate the waste heat. An electric fan was used to provide air into the system. A theoretical model was developed to predict the system performance. The model was found in good agreement with the experimental data.

Abstract: The characteristics of working medium is one of the important factors for organic Rankine cycle.The study is based on the waste heat of power plant,7 kinds working medium are selected,include R245fa, R600, R600a, R601a, R236fa, R236ea and RC318.ORC's thermodynamic cycle characteristics are calculated based on the first law of thermodynamics,then,compared the thermal efficiency,evaporating pressure and power ratio of different working medium.Results show that R245fa and R601a as the ORC system working medium have higher thermal efficiency and power ratio,and lower evaporating pressure than other five working medium,are ideal organic working medium to recycle flue gas waste heat of power plant.Secondly,R600 as system cycle working medium also has relatively good performance,can be the appropriate choice of working medium.

Abstract: Flue gas of boiler is a kind of great potential waste heat resource. Relatively high temperature of exhaust has caused a vast waste of energy and serious environmental thermal pollutions. To make a full and reasonable use of the heat resource, a simplified single-tube heat exchanger is introduced in this paper. Dry air and wet air with different temperatures transfer heat with flue gas in the same model. And the results show that heat near the inner wall exchanges more violently than any other space in the heater. For dry air, the higher temperature of the air enters into the heater, the lower heat transfer effect of the heater. Heat exchange effect of the wet air with 0.03 mole fraction of water is more higher than that of dry air in this model.

Abstract: Utilization of alternative fuels and utilization of waste heat has also become a major research area. This study reports on an investigation on a development of an energy converter of heat engine that converts energy from a waste heat flow process into acoustic power. The energy power converter operates with a temperature gradient imposed on a Celcor ceramic stack which then induces pressure oscillations. The system consists of a simple stainless steel pipe tube with a range of diameter open at one end. A waste heat gas is used to model a potential heat source from automobile engine. A two heat exchanger is required while copper plates are used as the ambient heat exchanger and hot heat exchanger. Effects on pressure oscillations have been observed with a calculated heat rate of 50 W at the stack. The system which operates at atmospheric pressure with air as the working fluid indicates a potential in utilizing the heat produced from waste heat automobile engine into making a new energy resource.

Abstract: The current worldwide trend of rapid economic development and increasing energy requirement in the transportation sector are one of many segments that is responsible for a growing share of fossil fuel usage. Supply and demand for fuel is accelerating prices and eventually will affect availability. The selected contemporary paper will address on how a prototype Stirling engine capable of reining in waste heat spilling out of the typical engine exhaust and its intensity level to oppose against the tyranny of inefficiency. Stirling engine systems are fuel flexible with respect to source of thermal energy and unprocessed waste heat that resulting in entropy rise can be harvested to power Ancillaries and increase overall efficiency. The preliminary prototype design and methodology follows process, heat to mechanical energy and latter to electrical energy. Experimental verification of analytical data was carried out and presented here. The shortcomings of these methods are highlighted and an alternative approach to solving particulars suggested.