Conference Agenda

Due to climate change, the range of outdoor temperature and humidity has expanded with the range of dew point temperature, thereby increasing the risk of condensation in buildings. In the mid-1980s, the problem of the risk of condensation occurring in unconditioned spaces during winter was recognized. In the 1990s, balcony expansion became popular, and the importance of ventilation and strengthening insulation at thermal bridge began to be highlighted due to the risk of condensation in balcony areas. In the 2000s and 2010s, as the number of curtain wall buildings increased and the insulation standards for walls and windows were strengthened, many evaluations were conducted on the anti-condensation performance of window and wall-slab joints, which are vulnerable to thermal bridges. Various studies have been conducted to solve the condensation problem through passive methods using existing building materials, such as precise construction, use of spacers insulation, installation of openings for ventilation, and improvement of window design and performance. In 2021, however, the number of applications for review of defects due to condensation from the top 10 large construction companies in Republic of Korea reaches 3,674, and more than 60% of them are judged to be actual defects, so damage due to condensation continues in various buildings.

Passive anti-condensation technology has difficulty responding to indoor dew point temperatures that change depending on the comfort range of occupants. For this reason, it is difficult to prevent deterioration of indoor air quality because of mold and bacteria as condensation occurs repeatedly under certain outdoor air conditions. Accordingly, in this study, through THERM 7.8, a heat transfer analysis simulation, and thermoelectric elements regression analysis formula, it was derived that areas where the indoor wall surface temperature in winter fell below the dew point temperature with operating time. Based on the simulation results, it was analyzed the applicability of active anti-condensation materials using thermoelectric technology, which can flexibly respond to the risk of condensation according to the changes of indoor and outdoor temperature and humidity, in building systems.

The average daily power consumption of thermoelectric elements per unit area was analyzed as 727.20 Wh/m²/day at the side wall, 1249.72 Wh/m²/day at the top of the front wall, and 1087.61 Wh/m²/day at the bottom of the front wall. Considering the installation area of the thermoelectric active anti-condensation materials, the annual power consumption in one apartment unit was 5.55 kWh/yr at the side wall, 9.54 kWh/yr at the top of the front wall, and 8.30 kWh/yr at the bottom of the front wall. Considering the health of occupants, such as mold and bacteria caused by continued condensation, thermoelectric active anti-condensation materials are expected to have excellent economic feasibility. In addition, since thermoelectric modules were installed at thermal bridges where large temperature differences occur, it is expected that energy harvesting technology can also be utilized based on the Seebeck effect during periods when the incidence of condensation is low.

The escalating demand for low-GWP, high-efficiency refrigerants in air conditioning and heat pump applications has driven the adoption of blends capable of meeting technical and performance criteria. Zeotropic compositions, characterized by temperature glide, may necessitate heat exchanger redesign to counter pinching effects. However, this unique property presents an opportunity for performance enhancement. Leveraging the refrigerant glide, particularly in areas where a constant saturation temperature cannot suffice, offers a promising avenue for improvement.

This investigation explores the use of multi-row coils to align the glide with the temperature lift of the air and introduces the use of a suction-line liquid-line heat exchanger (SLHX) to exploit the glide to improve evaporator performance. Thermodynamic properties of HFO-based refrigerants show a need to increase overall heat transfer area and compressor displacement to match COP and capacity of R410A. By designing heat exchangers around a cross-counter flow arrangement and proper circuitry it’s possible to achieve similar performance to R32. Through modeling, the study assesses the impact of SLHX on pure (R32) and zeotropic (R454C) refrigerants. The results demonstrate significant performance enhancement for R454C, attributed to the relocation of the higher temperature saturation region from the evaporator to the SLHX. This enables operation at higher suction pressures without encountering evaporator pinching. The findings underscore the potential of SLHX in optimizing refrigerant performance, particularly in zeotropic compositions, for enhanced efficiency in air conditioning and heat pump systems.

Recent theoretical research shows it is possible to convert effectively ambient temperature heat in clean refrigeration, heating and work, using the synergy of absorption and hybrid compression technologies. This paper considers work and refrigeration aspects, only. The new technology, named Mother & Father Hybrid Compression (M&F), may challenge known nuclear and clean renewable energy technologies like solar, wind, photovoltaics, biomass. The M&F technology might be capable to produce mechanical or electrical energy up to 1.0 MJ work / kg refrigerant, most ecologically 24 hours / day and 365 days / year in most world regions with -63 to +75 C deg. ambient temperatures. The ambient temperature heat source is external sink source, as well. The paper gives M&F flow-charts and working operation results. Two important M&F aspects relate to its put in work order. First, M&F may be used in terrestrial, maritime and space stationary and mobile applications. Second, given the ambient heat source is mostly of sensible type and much less of latent type, the mobile applications may be confronted with limited specific capacity, especially when the heat source is air, unless storage of M&F energy produced would not be considered. The present work shows that, even in these cases, it might be possible to benefit of M&F direct application, for instance for car transportation. The work gives two curves families of air and water mass flow rates, kg/s, having -54 to +49 C degrees and 0 to +49 C degrees heat temperature, respectively. Results base on sensible heat extraction from heat sources only and are plotted for 1 kW power and 1 C degrees air and water extraction temperature difference. For higher power and ambient temperature differences, results of curves families alter by appropriate factors. In case of air heat supply in temperate and warm climates, the required mass flow rate is cca. 1.2 to 1.35 kg/s. In case of water heat supply, mass flow rates are by cca. 7 times smaller as compared to those of air, so work capacity of M&F mobile plants can be considerably higher and fluvial and maritime navigation is favored. Conclusions of M&F technology use are: i) extracting heat from ambient can decrease significantly the global warming; ii) it extends distributed clean energy production as compared to present times; iii) applications might be feasible especially in case of water use as ambient heat source, with very positive impact on maritime navigation.

The author elaborated recently the Mother & Father Hybrid Compression Technology, M&FHC. So far, a power cycle plant produced mechanical work exclusively by having the ambient temperature heat source as sink source and a higher temperature than the sink source as heat source. Such a plant named (super-) ambient power plant or AP plant, e.g. Rankine and Rankine-Gas Turbine plants. Unlike AP, M&FHC emphasizes a new concept of power plants, capable to produce mechanical work by using the ambient temperature source as heat source and an artificially created source, of temperature below that of the ambient temperature, as sink source. Such plant named sub-ambient power plant, or SAP plant. Except the hydro-power, wind-and wave-farms and possibly other few small clean power technologies, all the AP plants producing world major power base on operation of (bottoming) steam Rankine cycle (SRC), supplied by fossil or non-pollutant fuels. Roughly, the SRC plants condensers evacuate to ambient sink a huge quantity of heat, equal approximately to the power produced. Most people involved in energy consider planet global warming is the result of CO2 pollution caused by SRC plants burning fossil fuels. This picture is not realistic to a good extent. Indeed, a large plant category are considered “nonpolluting” because do not burn hydrocarbon fuels. To this category belong e.g. the actual Rankine plants powered by nuclear, biomass burning, or future fusion technology. However, they pollute the planet simply by rejecting in the atmosphere the condensing heat we mentioned earlier. The energy involved people attempt to solve the global warming replacing CO2 polluting plants with as much as more power plants belonging to the “nonpolluting” category, but this is far from being the solution. Indeed, first, because the hydrocarbon burning plants are most efficient and second, these plants are replaced by less efficient plants, which heat rejection of in the ambient could be even more pollutant, because CO2 is blocking in global warming all the Earth natural cooling channels. Because the global warming evolves quick, we must find rapidly a realistic solution. The solution could come from the introduction of the SAP technology. The author proposed lately for the first time an AP & SAP energetic coupling. The AP can be either of “nonpolluting” or polluting type. The AP & SAP coupling applies until SAP replaces the AP in most possible applications. In the AP & SAP synergy, SAP recovers as heat source the condensing heat rejected by AP to ambient sink, of ambient temperature. The work presents a simple model of AP&SAP synergy and model outputs for AP, M&FHC based SAP and AP&SAP electrical efficiencies obtained for four SRC plants powered by nuclear, biomass and fuel of hydrocarbon nature, or coming from the future fusion. Results show the AP&SAP synergy efficiency is approximately 1.51 – 2.21 times higher as compared to that of AP plant. This result is a consequence of the AP&SAP synergy work, which is by approximately 1.49 - 2.35 times higher as compared to that produced by AP plant alone.