The policy of sustainable development seeks to improve energy efficiency of industrial equipment. Efforts to improve energy efficiency also apply to the paint shops, where the recovery of waste heat is sought. The main source of a large amount of low-temperature waste heat in the paint shop is the spray booth. The second place where a large amount of low temperature waste heat is released is the room where the compressed air is prepared. Low energy efficiency of air compressors requires a large electric power supply. As a result, the emitted large heat fluxes become waste energy of the technological process. Heat is equivalent to up to 93% of the electric power supplied in the air compression process. There are solutions for recovering heat from compressors coming from the oil cooling water, but then the waste heat from the cooling of the compressed air and from the electric motor is released into air in the room. A method for recovering low-temperature waste heat from the air preparation room by means of an air-source heat pump has been proposed. An energy balance of the air compression and dehumidification process for the paint shop was made. A Matlab’s built-in numerical model includes air compressor and dehumidifier, heat recovery and accumulation for the purposes of use in the spray booth. A simulation experiment was carried out on the effectiveness of heat recovery from the air preparation room. The use of combined energy management in paint shops was proposed.
In the paper presented are studies on the investigation of the capillary forces effect induced in the porous structure of a loop heat pipe using water and ethanol ad test fluids. The potential application of such effect is for example in the evaporator of the domestic micro-CHP unit, where the reduction of pumping power could be obtained. Preliminary analysis of the results indicates water as having the best potential for developing the capillary effect.
Turbine stages can be divided into two types: impulse stages and reaction stages. The advantages of one type over the second one are generally known based on the basic physics of turbine stage. In this paper these differences between mentioned two types of turbines were indicated on the example of single stage turbines dedicated to work in organic Rankine cycle (ORC) power systems. The turbines for two ORC cases were analysed: the plant generating up to 30 kW and up to 300 kW of net electric power, respectively. Mentioned ORC systems operate with different working fluids: DMC (dimethyl carbonate) for the 30 kW power plant and MM (hexamethyldisiloxane) for the 300 kW power plant. The turbines were compared according to three major issues: thermodynamic and aerodynamic performance, mechanical and manufacturing aspects. The analysis was performed by means of the 0D turbomachinery theory and 3D computational aerodynamic calculations. As a result of this analysis, the paper indicates conclusions which type of turbine is a recommended choice to use in ORC systems taking into account the features of these systems.
The increase of ship’s energy utilization efficiency and the reduction of greenhouse gas emissions have been high lightened in recent years and have become an increasingly important subject for ship designers and owners. The International Maritime Organization (IMO) is seeking measures to reduce the CO2emissions from ships, and their proposed energy efficiency design index (EEDI) and energy efficiency operational indicator (EEOI) aim at ensuring that future vessels will be more efficient. Waste heat recovery can be employed not only to improve energy utilization efficiency but also to reduce greenhouse gas emissions. In this paper, a typical conceptual large container ship employing a low speed marine diesel engine as the main propulsion machinery is introduced and three possible types of waste heat recovery systems are designed. To calculate the EEDI and EEOI of the given large container ship, two software packages are developed. From the viewpoint of operation and maintenance, lowering the ship speed and improving container load rate can greatly reduce EEOI and further reduce total fuel consumption. Although the large container ship itself can reach the IMO requirements of EEDI at the first stage with a reduction factor 10% under the reference line value, the proposed waste heat recovery systems can improve the ship EEDI reduction factor to 20% under the reference line value.
Maritime transport is facing a set of technical challenges due to implementation of ecological criterions on 1st Jan. 2020 and 2021 by the International Maritime Organization. The advantageous properties of natural gas (NG) as fuel in conjunction with dual-fuel (DF) internal combustion engines (ICE) potentially enables the fulfilment of all criterions. Moreover the 2020 global sulfur cap in combination with its low content in NG potentially enables to recover higher rates of waste heat and exergy of exhaust gas without the risk of low temperature corrosion. In this study the influence of sulfur content in NG and pilot fuel oil (PFO) on the sulfuric acid condensation temperature was investigated in order to determine the rate of waste heat (quantity) and exergy (quality) of four-stroke DF IC engine’s exhaust for 50%, 85% and 100% of engine load. Determined parameters were compared with two sets of reference values calculated for the same engine: a) fueled with NG and PFO with fixed minimum exhaust temperature set as 423.15 K, b) fueled with 3.5% sulfur mass fraction fuel oil only with variable minimum exhaust gas temperature. The results show that the assumption of case a) can lead to significant reduction of recovered rates of exhaust waste heat and exergy in the ranges of 10% to 24% and 43% to 57%, respectively. Higher values were obtained for case b) where the ranges of unrecovered rate of heat and exergy achieved 20% to 38% and 60% to 70%.
The paper illustrates a case study of fluid selection for an internal combustion engine heat recovery organic Rankine cycle (ORC) system having the net power of about 30 kW. Various criteria of fluid selection are discussed. Particular attention is paid to thermodynamic performance of the system and human safety. The selection of working fluid for the ORC system has a large impact on the next steps of the design process, i.e., the working substance affects the turbine design and the size and type of heat exchangers. The final choice is usually a compromise between thermodynamic performance, safety and impact on natural environment. The most important parameters in thermodynamic analysis include calculations of net generated power and ORC cycle efficiency. Some level of toxicity and flammability can be accepted only if the leakages are very low. The fluid thermal stability level has to be taken into account too. The economy is a key aspect from the commercial point of view and that includes not only the fluid cost but also other costs which are the consequence of particular fluid selection. The paper discusses various configurations of the ORC system – with and without a regenerator and with direct or indirect evaporation. The selected working fluids for the considered particular power plant include toluene, DMC (dimethyl carbonate) and MM (hexamethyldisiloxane). Their advantages and disadvantages are outlined.