The Effects of Fin Spacing and Tube Outer Diameter of Evaporator on System Performance in Heat Pump Tumble Dryers

In heat pump tumble dryers, moisture separates from the laundry and leaves the dryer system at the evaporator. Moist air goes out the drum and enters the evaporator whose outer surface is below the dew point temperature. Air cools and then leaves its moisture. At the airside of the evaporator the wet surface develops and simultaneous heat-mass transfer occurs. Fin-and-tube heat exchangers are used as evaporators in household heat pump tumble dryers. In addition to optimum operating conditions, optimum evaporator geometry can significantly affect system performance. In this study, a model was developed for household heat pump tumble dryer. The model was validated by experimental data collected from the literature. MATLAB software was used in programming, and fluid properties were taken from Refprop software. The model was run with different fin spacing (2–5 mm) and tube outer diameter (6–12 mm) for evaporator, whereas operating conditions and all other geometrical parameters stayed the same. Then, coefficient of performance (COP), moisture extraction rate (MER), and specific moisture extraction rate (SMER) were calculated. As a result, the effects of fin spacing and tube outer diameter of evaporator were determined depending on the input characteristics of the dryer model. In the working range, SMER was changed up to 20% and 15% depending on the fin spacing and the tube outer diameter of evaporator, respectively

The Effects of Gas Cooler Inlet Pressure on System Performance in Heat Pump Tumble Dryers

Heat pumps working with CO2 as a refrigerant have low energy consumptions if right application areas and operating conditions are selected. The use of CO2 in heat pump dryers is feasible if operating temperatures are appropriate. In heat pump dryers working with CO2 according to the transcritical cycle, one of the most important operating conditions is optimum gas cooler inlet pressure, which gives the maximum coefficient of performance (COP). In this study, a model was developed by using MATLAB software for heat pump tumble dryer working with CO2. The model was validated by experimental data taken from existing literature. Then, COP, moisture extraction rate (MER), and specific moisture extraction rate (SMER) were found by running the model at different gas cooler inlet pressures (80–140 bars). All results were calculated in the same geometry for evaporator, gas cooler, and compressor. Thus, effects on the results of variation of the geometrical features were eliminated. Optimum gas cooler inlet pressure was determined as 100 bars for the system with data input to the model. In the optimum gas cooler inlet pressure working condition, SMER increased 24% and 12% by comparison with 80 bars and 140 bars gas cooler inlet pressure, respectively

Growing Out of the Experience: How Subjective Experiences of Effort and Learning Influence the Use of Interleaved Practice

In higher education, many students make poor learning strategy decisions. This, in part, results from the counterintuitive nature of effective learning strategies: they enhance long-term learning but also cost high initial effort and appear to not improve learning (immediately). This mixed-method study investigated how students make learning strategy decisions in category learning, and whether students can be supported to make effective strategy decisions through a metacognitive prompt, designed to support accurate monitoring of effort and learning. Participants (N = 150) studied painting styles through blocked and interleaved practice, rated their perceived effort and perceived learning across time, and chose between either blocked or interleaved practice. Half of the participants (N = 74) were provided with a metacognitive prompt that showed them how their subjective experiences per strategy changed across time and required them to relate these experiences to the efficacy of learning strategies. Results indicated that subjective experiences with interleaved practice improved across time: students’ perceived learning increased as their perceived effort decreased. Mediation analysis revealed that the increased feeling of learning increased the likelihood to select interleaved practice. The percentage of students who chose interleaved practice increased from 13 to 40%. Students’ learning strategy decisions, however, did not benefit from the metacognitive prompt. Qualitative results revealed that students initially had inaccurate beliefs about the efficacy of learning strategies, but on-task experiences overrode the influence of prior beliefs in learning strategy decisions. This study suggests that repeated monitoring of effort and learning have the potential to improve the use of interleaved practice

How social challenges affect children’s regulation and assignment quality in hypermedia: a process mining study

The present study investigated the extent to which 18 dyads in 5th and 6th grade, who experienced low levels of social challenge, differed from 12 dyads who experience high levels of social challenge in terms of the quality of their written assignment, as well as the frequency and sequential pattern of their cognitive, metacognitive, relational, and off-task activities during a collaborative hypermedia assignment. Sequential analyses were performed by means of process mining with a fuzzy miner algorithm. Results showed that assignment quality was higher for low social challenge dyads. In addition, these more successful dyads showed more cognitive processing activities, more high-cognition, and fewer off-task activities. In terms of their process models, low and high challenge dyads showed marked differences. More specifically, high social challenge dyads showed a vicious cycle of social challenges and off-task behaviors, whereas low social challenge dyads engaged in high-cognition. In addition, for low challenge dyads, but not high challenge dyads, the various metacognitive activities were closely connected to each other. These findings indicate that social challenges not only affect assignment quality, but also fundamentally affect the overall learning process

Uterine smooth muscle tumor of uncertain malignant potential: fertility and clinical outcomes.

In this study, we aimed to evaluate the clinicopathological features, obstetric, and oncological outcomes of patients diagnosed with a uterine smooth muscle tumors of uncertain malignant potential (STUMP)

Uterine smooth muscle tumor of uncertain malignant potential: fertility and clinical outcomes

Objective: In this study, we aimed to evaluate the clinicopathological features, obstetric, and oncological outcomes of patients diagnosed with a uterine smooth muscle tumors of uncertain malignant potential (STUMP). Methods: A dual-institutional, database review was carried out to screen patients with STUMP who were treated with upfront surgery between January 2006 and December 2017. Data including age at the time of diagnosis, recurrence rate, disease-free survival, overall survival, and fertility outcomes were retrospectively analyzed. Results: Fifty-seven patients with STUMPs were included in the study. The median age at the time of diagnosis was 42 (range, 16 to 75) years. The median follow-up was 57 (range, 16 to 125) months. Eight patients (14\%) had recurrence during follow-up. Recurrent STUMPs were seen in seven patients and leiomyosarcoma after 14 months in one patient. Seven patients with a recurrent STUMP survived, while the remaining patient died. Recurrence rates were similar for women who underwent myomectomy and those who underwent hysterectomy. The presence of uterine localization of tumor (subserosal vs intramural-submucosal) statistically significantly affected recurrence rates (odds ratio=5.72; 95\% confidence interval=1.349-24.290; p=0.018). Ten of 27 patients who underwent myomectomy for uterine myoma had fertility desire. Seven pregnancies were recorded. Conclusions: Our study results suggest that fertility-sparing approaches are feasible in patients with STUMP, although recurrence may be seen