Rational Heat Schemes Using Condensing Boilers in Local Heat Supply Systems

Within the framework of this publication, thermal diagrams of autonomous heat supply systems using condensing heat generators are considered. The insignificant Russian experience of using small condensation boilers in residential construction shows that it is often used to simply replace traditional equipment with condensation technology in existing (or traditionally used) heat schemes, for example, with protection of the boiler from “cold return” by recirculating heat carrier or installing a hydraulic regulator. The consequence of this is almost completely lost the effect of the use of condensing boilers. At the same time, even using the heating temperature schedule of quality regulation 80-60°C and applying water heating to the DHW target up to 45°C you can achieve the effect of the boiler operation in the condensation mode, depending on the construction area, up to 75% of the total working time per year, generating about 70% of thermal energy in the annual cycle. However, it must be borne in mind that the efficiency of the condensing boiler is determined by the part of the latent heat of water vapor in the combustion products, which can be obtained with partial condensation. If this part is small, for example, when cooling the flue gases to 50-45°C (on gas), then the efficiency gain is only 1-3%.

Size-Segregated Atmospheric Humic-Like Substances (HULIS) in Shanghai: Abundance, Seasonal Variation, and Source Identification

Humic-like substances (HULIS) are of great interest due to their optical and chemical characteristics. In this study, a total of 180 samples of atmospheric particulate matter (PM) of different sizes were collected from summer 2018 to spring 2019, in order to analyze the size distribution, to investigate the seasonal variation and then to identify the key sources of HULIS. The annual mean concentration of HULIS in the total suspended particulates reached 5.12 ± 1.42 μg/m3. The HULIS concentration was extremely higher in winter (8.35 ± 2.06 μg/m3) than in autumn (4.88 ± 0.95 μg/m3), in summer (3.62 ± 1.68 μg/m3) and in spring (3.36 ± 0.99 μg/m3). The average annual ratio of water-soluble organic carbon (WSOC) to OC and the ratio of HULIS to WSOC reached 0.546 ± 0.092 and 0.56 ± 0.06, respectively. Throughout the whole year, the size distributions of WSOC and HULIS-C were relatively smooth. The peaks of WSOC appeared at 1.8~3.2 μm and 0.56~1.0 μm, while the peaks of HULIS-C were located at 3.2~5.6 μm, 1.0~1.8 μm and 0.18~0.32 μm. The distribution of the HULIS particle mode was similar in spring, summer and autumn, while there was a lower proportion of the coarse mode and a higher proportion of the condensation mode in winter. By using the comprehensive analysis of principal component analysis (PCA), air mass backward trajectories (AMBTs) and fire point maps, key sources of WSOC and HULIS in Shanghai were identified as biomass combustion (48.42%), coal combustion (17.49%), secondary formation (16.07%) and vehicle exhaust (5.37%). The remaining part might be contributed by crustal dust sources, marine sources and/or other possible sources. This study provides new insight into the characteristics and size distribution of HULIS in Shanghai, thereby providing a practical base for further modeling.

Physical and chemical constraints on transformation and mass-increase of fine aerosols in northeast Asia

Over the past few decades, northeast Asia has suffered from the extreme levels of PM2.5 (particulate matter with an aerodynamic diameter smaller than 2.5 μm). Despite extensive efforts and the scientific advances in understanding PM2.5 pollution, the fundamental mechanisms responsible for the occurrence of high PM2.5 concentrations have not been comprehensively understood. In this study, we investigated the physical and chemical drivers for the formation and transformation of atmospheric particles using a four-year dataset of nanoparticle number size distributions, PM2.5 chemical composition, gaseous precursors, and meteorological variables in northeast Asia outflows. The empirical orthogonal function (EOF) analyses of size-separated particle numbers extracted two modes representing a burst of nanoparticles (EOF1) and an increase in PM2.5 mass (EOF2) associated with persistent anticyclone and synoptic-scale stagnation, respectively. The vertical structure of the particles demonstrated that the synoptic conditions also affected the daily evolution of boundary layer, promoting either the formation of nanoparticles through deep mixing or conversion into accumulation-mode particles in shallow mixed layers. In the haze-development episode equivalent to EOF2 during the KORUS-AQ (KORea-US Air Quality) campaign, the PM2.5 mass reached 63 μg m−3 with the highest contribution from inorganic constituents, which was accompanied by a thick coating of refractory black carbon (rBC) that linearly increased with condensation-mode particles. This observational evidence suggests that the thick coating of rBC resulted from an active conversion of condensable gases into particle-phase on the BC surface, thereby increasing the mass of the accumulation-mode aerosol. Consequently, this result complies with the strategy to reduce black carbon as a way to effectively mitigate haze pollution as well as climate change in northeast Asia.

Experimental investigation of a high efficiency electric heater and dehumidifier prototype unit

In this paper the principle of operation and preliminary laboratory measurements of a prototype of a high-efficiency electrical air heater unit is presented. Unlike conventional heaters, which apply Joule-heat formed by electrical resistance, the developed device uses thermoelectric modules for heating ambient air. Just like in case of resistance heaters, most of the heat is produced as a result of the internal ohmic resistance of the thermoelectric module (resistance heating), however, in case of appropriate air conditions our device is capable of transforming the latent heat of the air moisture into heat energy. In case of condensation mode, some of the moisture condensates on the cold side of the module while its latent heat is transferred to the hot side of the module where it heats the dried air. In this mode, the heating efficiency of the device (e.g., the ratio of the heat added to air and the consumed electricity) is over unity. Following the idea and basic equations of the operation of this device, the results of the laboratory measurements in a climate test chamber is presented.

Modelling of Soot Formation and Experimental Study for Different Octane Number Fuels in Dual Fuel Combustion Engine With Diesel

This work investigates the effects of low reactivity fuel (LRF) on reactivity controlled compression ignition (RCCI) engine with fossil diesel. RCCI mode of combustion is a low temperature combustion (LTC) strategy which reduces both oxides of nitrogen (NOx) and soot emissions simultaneously. Syngas and methanol can be obtained from renewable biological resources and conventional coal. LRF (methanol, syngas and gasoline) has been supplied to the engine along with intake air and diesel is injected to initiate the combustion process. Test engine has been operated for different dual fuel modes at constant engine speed (1500 rpm) and load (80%). Closed cycle combustion simulations have been performed to complement the experimental results and in-cylinder dynamics. Particle size mimic (PSM) model has been used to investigate the soot particle number and mass-size distributions and mean particle size. Results confirmed that maximum gross indicated thermal efficiency (38%) has been observed in gasoline/diesel dual fuel mode. Compared to gasoline/diesel dual fuel mode, about 74% and 86%, lower soot and NOx emissions have been observed for methanol/diesel dual fuel mode, while about 46% and 52% lower soot and NOx emissions have been found in syngas/diesel mode. About 53% higher carbon monoxide emission has been observed for syngas/diesel case as compared to gasoline/diesel case. Predictions from soot modelling reveal that condensation mode, surface growth mode and nucleation mode particles are dominant in methanol, syngas and gasoline/diesel dual fuel modes respectively. Bigger primary soot particles (diameter > 35 nm, nanometre) have been observed for methanol/diesel mode and the gasoline/diesel mode shows a smaller size of primary particles.

Resource-saving thermodynamic cycles in liquid hydrocarbon fuel storage technology

Resource-saving thermodynamic cycles for material and energy flows in the technology of storing liquid hydrocarbon fuel in tanks using a vapor compression heat pump are proposed, which reduce the loss of fuel resulting from evaporation. The heat pump is equipped with a two-section evaporator, the working and reserve sections of which alternately operate in condensation and regeneration modes, respectively. Vapors of hydrocarbon fuel from the tank are discharged to the evaporator section operating in condensation mode. The water contained in the fuel vapor condenses on the heat ex-change surface in the form of an ice crust, and the condensed fuel separated from the water is discharged into an interme-diate tank and returned to the storage tank. The condensation heat of the refrigerant in the condenser is used to heat the intermediate coolant, which is sent to defrost the section of the evaporator operating in the regeneration mode. After this section, the spent intermediate coolant is returned to the condenser in the closed thermodynamic cycle mode. The water formed during defrosting is sent to the biological treatment stage. Thus, real conditions are created for increasing the ener-gy efficiency and environmental safety of the technology for storing liquid hydrocarbon fuel in tanks with maximum con-densation of the vapors resulting from evaporation.

Increasing the reliability and manoeuvrability of the CCGT when operating in the variable part of the power consumption schedules by switching the CCGT steam turbine to the motor mode

The report is devoted to the problem of increasing the reliability and manoeuvrability of the CCGT when it operates in power control modes of the power system. The generalized results of research on improving the reliability and expanding the adjustment range of the PGU-450 based on the use of bypass steam distribution, reducing the duration of start-up operations and increasing the loading speed of the steam turbine and CCGT in general in the modes of CCGT power reserve during the night load gap by transferring the CCGT steam turbine to the motor mode when the CCGT operates in the condensation mode or in the heating mode according to the GTU-CHP scheme are presented. Additional advantages of the motor mode are noted: improved reliability of the steam turbine due to the elimination of cyclic temperature fluctuations of its steam inlet valves and vibrations in the last stages of the low-pressure cylinder and the possibility of operating the steam turbine generator in the synchronous compensator mode.

Initiation of condensation of toluene and octane vapours on a Si surface

The use of the zeta adsorption isotherm in determining the condensation mode of toluene on silicon.