112,501 research outputs found
Study of the Effects of Microgroove Geometry on Frost Structure
No full textThe variation in the frost structure on a number of microgrooved brass surfaces is examined through an experimental study. The microgrooved samples are 45 mm x 45 mm in dimension with a broad range of groove dimensions. Frost is grown on these microgrooved surfaces under natural convection for a range of plate temperature (-8 to -18o C) and relative humidity (30-70%) conditions. The frost structure on the microgrooved surfaces, especially at the early stages of frost formation, is found to be significantly affected by the groove geometry (i.e. groove depth and pillar width). Coalescence of the condensed and hence frozen droplets, covering multiple pillars and grooves, is found to occur more frequently on the surfaces with shallow grooves and/or narrow pillars. For surfaces with intermediate groove depth and pillar width, a regular (brick-wall-like) frost pattern on the pillar surface is observed. Thickness and density of frost layer on the microgrooved surfaces are also found to vary with the dimension of the grooves in frost cycles up to 4 hours long. The relationships between frost structure, frost properties, and frost melt-water drainage is discussed, emphasizing the importance of these morphological features
Frost Formation on Fan-Supplied Tube-Fin Evaporators: A Visual and Numerical Analysis
No full textThis paper presents an experimental and numerical study to evaluate the thermal-hydraulic performance of light commercial capacity evaporators operating under frosting conditions. A tube-fin heat exchanger was tested on a closed-loop wind-tunnel considering the fan performance. A visual analysis of the frost formation processes was carried out to compare the frost layer morphology in different conditions. A mathematical model was developed and the numerical results were compared with the experimental accumulated mass of frost, air flow rate and cooling capacity, with all the predictions falling within the experimental band of uncertainties. Based on this comparison, a frost density correlation was proposed for a typical range of light commercial refrigeration applications. The results show evaporator cooling capacity reductions up to 40% due to frost formation process. Moreover, the effects of air flow reduction and low conductivity frost layer on the overall thermal resistance were analyzed, when it was found that the former is the main cause of the cooling capacity reduction under frosting conditions
Spiro Agnew speaks with David Frost
No full textSpiro Agnew, Vice President under Richard Nixon, holds an in-depth interveiw with David Frost about his own combat experiences, his education, and that of his children
Avaliação de métodos para quantificar geada em evaporadores de refrigeradores frost-free
No full textDissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-Graduação em Engenharia Mecânica, Florianópolis, 2015.Em evaporadores no-frost o acúmulo de geada é inevitável. Por degenerar a capacidade de refrigeração do sistema, degelos periódicos são necessários. Esse processo normalmente ocorre através do acionamento de um resistor elétrico e tem impacto negativo para o sistema, pois aumenta a carga térmica e causa variação da temperatura no refrigerador. Portanto, em um refrigerador é normalmente desejada a ocorrência de degelo somente quando necessário, para manter a eficiência do sistema de refrigeração. Entretanto, o atual controle desse processo permite que degelos desnecessários ocorram, não atuando de forma inteligente. Em vista disso, este trabalho tem por objetivo estudar possibilidades de identificação da quantidade de geada presente nos evaporadores para que o degelo possa ser controlado pela demanda. Para isso, investigaram-se experimentalmente diversas possibilidades. Deu-se enfoque às possibilidades que não exigem inserção e utilização de mais transdutores nos refrigeradores. Para os ensaios, construiu-se bancada própria e um refrigerador de modelo comum foi adaptado permitindo a visualização do processo. Testaram-se soluções baseadas na perda de carga do escoamento de ar sobre o evaporador, na eficiência da troca térmica do evaporador e também na evolução das temperaturas do evaporador e suas consequências, tais como a variação de resistência elétrica do resistor de degelo e a do enrolamento do motor do ventilador. Alguns transdutores capacitivos, indutivos e ópticos também foram avaliados. Os melhores resultados foram obtidos nas soluções baseadas na evolução de temperaturas. Um transdutor de fluxo de calor instalado permitiu analisar a influência da geada. Os resultados mostraram a degradação do coeficiente de transferência de calor devido à presença da geada, porém de maneira insuficiente para indicar a quantidade de geada. A possibilidade baseada na análise da dinâmica de variação das temperaturas frente à perturbação do sistema foi validada. Porém, o conceito encontrou obstáculo para diferenciar quantidades menores de geada depositada. Ao final deste trabalho não foi possível encontrar um método eficiente para o presente problema.Abstract : In no-frost evaporator, frost accumulation is unavoidable. Since this accretion depletes the cooling capacity of the refrigeration system, defrosts must be periodically carried out. This process is usually made by electrical heaters but it has a negative impact for the system because it increases the thermal load, and also causes temperature variation in the refrigerator. For this reason, in a refrigerator, it is normally desirable to defrost only as necessary to maintain an efficient cooling system. However, the current control of this process allows unnecessary defrosts, and not intelligent actions. Therefore, the present work aims to study possibilities to identify amount of frost accumulated in evaporators, so that process of melting can be controlled by demand. Because of this, some solutions were experimentally investigated. The main focus were the possibilities that do not require insertion and use of more transducers in refrigerators. In order to test, an experimental apparatus was assembled; a common model of refrigerator was adapted allowing the visualization of the process. Solutions based on the pressure loss of the airflow over the evaporator, the heat exchange efficiency of the evaporator; and the evolution of evaporator temperatures and its consequences, such as the variation of the electrical resistance of the heater and the fan motor winding, were tested. Some sensors, based in capacitive, inductive and optical principle, were also evaluated. The best results were obtained in solutions based on the temperature development. A heat flow transducer installed in coil allowed analysis of the frost. The results showed the degradation of heat transfer coefficient due to the presence of frost, but insufficiently to indicate the amount of frost. The option based on the analysis of the dynamics of temperatures variation by a system disturb was validated. However, the concept encountered an obstacle in real operation condition of refrigerator. At the end of this work was not possible to find an efficient method to this problem
The Frost Multidimensional Perfectionism Scale revisited: More perfect with four (instead of six) dimensions
No full textThe Frost Multidimensional Perfectionism Scale (FMPS; Frost, Marten, Lahart & Rosenblate, 1990) provides six subscales for a multidimensional assessment of perfectionism: Concern over Mistakes (CM), Personal Standards (PS), Parental Expectations (PE), Parental Criticism (PC), Doubts about actions (D), and Organization (O). Despite its increasing popularity in personality and clinical research, the FMPS has also drawn some criticism for its factorial instability across samples. The present article argues that this instability may be due to an overextraction of components. Whereas all previous analyses presented six-factor solutions for the FMPS items, a reanalysis with Horn's parallel analysis suggested only four or five underlying factors. To investigate the nature of these factors, item responses from N = 243 participants were subjected to principal component analysis. Again, parallel analysis retained only four components. Varimax rotation replicated PS and O as separate factors, whereas combining CM with D as well as PE with PC. Consequently, the present article suggests a reduction to four (instead of six) FMPS subscales. Differential correlations with anxiety, depression, parental representations and action tendencies underscore the advantage of this solution
Frost, W G, 428286
No full textThis record was harvested from a previous catalogue system and will be withdrawn in 2025. Information in this record may be superseded or incomplete. Visit this record in UMA's new catalogue at: https://archives.library.unimelb.edu.au/nodes/view/386436Surname: FROST. Given Name(s) or Initials: W G. Military Service Number or Last Known Location: 428286. Missing, Wounded and Prisoner of War Enquiry Card Index Number: 57085.208206
Item: [2016.0049.18729] "Frost, W G, 428286
Frost, Elbridge G.
No full textCarte de Visite of Elbridge G. Frost, 2nd Maine Infantry, Company D, also 1st Maine Heavy Artillery, Company E; From the MacDonald Collectionhttps://digitalmaine.com/arc_civilwarportraits/2175/thumbnail.jp
Frost, Elbridge G.
No full textCarte de Visite of Elbridge G. Frost, 2nd Maine Infantry, Company D, also 1st Maine Heavy Artillery, Company E; From the MacDonald Collectionhttps://digitalmaine.com/arc_civilwarportraits/2175/thumbnail.jp
Modelagem semi-empírica de um refrigerador frost-free sujeito à abertura de portas
No full textDissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-Graduação em Engenharia Mecânica, Florianópolis, 2013.O projeto de refrigeradores domésticos é focado não somente na redução do consumo de energia em condições normalizadas, mas também em condições reais de operação, quando as portas dos compartimentos refrigerados são abertas periodicamente. Nesse caso, há transporte de umidade para os compartimentos refrigerados com consequente formação de geada sobre o evaporador, redução da vazão de ar e elevação no tempo de funcionamento do compressor. O efeito de tais fenômenos deve ser considerado para o adequado projeto dos componentes assim como para a definição de estratégias de controle do produto. A robustez do produto à formação de geada é geralmente estudada através de ensaios experimentais complexos, demorados e dispendiosos. Tal cenário favorece o uso de modelos matemáticos, embora nenhum dos modelos disponíveis na literatura seja capaz de simular o comportamento de um refrigerador doméstico submetido a ciclos de aberturas de portas e a consequente formação de geada sobre as superfícies do evaporador. Para eliminar essa lacuna, desenvolveu-se um modelo matemático para simular o comportamento transiente de um refrigerador doméstico sujeito a condições típicas de um teste de robustez à formação de geada. Para tanto, adotou-se uma abordagem semi-empírica, onde os componentes do refrigerador foram modelados com base em trabalhos disponíveis na literatura. Alguns dos parâmetros empíricos associados aos modelos desses componentes foram derivados de resultados experimentais obtidos com o próprio refrigerador. As estimativas do modelo foram devidamente validadas contra dados experimentais. O desvio máximo observado na previsão da evolução temporal da vazão mássica de refrigerante, da potência consumida e das pressões de evaporação e condensação foi de ±10%, da perda de carga no evaporador de ±20%, da massa de geada acumulado no evaporador de ±30% e das temperaturas dos compartimentos refrigerados de ±2ºC. Além disso, o modelo foi utilizado para estimar o comportamento de variáveis não facilmente mensuráveis tais como a evolução temporal da posição da fronteira entre as regiões bifásica e superaquecida no evaporador, da densidade e espessura da camada de geada e da distribuição da massa de geada e da perda de carga em cada fileira do evaporador.Abstract : Modern refrigerator design is aimed not only at energy savings but also at product robustness to evaporator frosting. Whilst the former is evaluated by means of standardized test procedures, the latter is assessed by testing the refrigerator under real usage conditions, when the doors are opened in a regular basis, allowing moisture to enter the refrigerated compartment and, consequently, frost to accumulate on the evaporator surface. As the frost layer grows, the air-side pressure drop rises, reducing the air flow rate and, therefore, the evaporator capacity. As a consequence, the compressor is driven to run longer cycles, thus increasing the energy consumption. The laboratory procedures required for product assessment and development rely on costly and time consuming experiments. Albeit it has been advocated that the adoption of simulation models may aid the product development process, there is no model available in the open literature which is capable of simulating the refrigerator performance under door-opening and frost build-up conditions. Therefore, a mathematical model for simulating the transient behavior of a domestic refrigerator in such conditions has been advanced in this work. A first-principles simulation model was put forward for the refrigeration loop, whereas a semi-empirical approach was adopted for the refrigerated compartment, in such a way that the key empirical parameters were obtained by testing the refrigerator in an environmental chamber. The model was validated against experimental data, when it was found that its predictions for power consumption and refrigerant mass flow rate fell within a ±10% error band, its predictions for accumulated frost mass were within a ±20% error band, and its predictions for compartment air temperatures were within a ±2K error band. The model is also capable of predicting the behavior of some non-measurable variables, such as the time evolution of the liquid-vapor to vapor transition point of the refrigerant in the evaporator, the density and thickness of the frost layer over the different rows of the evaporator and also the contribution of each of these rows on the air side pressure drop on the evaporator
'Crisis in Ohio' article
No full textArticle titled "The Crisis in Ohio" by Maria G. Frost, which calls for a revision of the Ohio Constitution in favor of women's suffrage. Frost couches her argument in religious and patriotic terms in support of "self government" for women. Maria Goodell Frost (1826-1899) was the daughter of William Goodell, a noted abolitionist and temperance advocate from New York. She supported both of these reform movements, and was active in support of women's suffrage.
This item comes from the Frances Jennings Casement Papers, a manuscript collection comprised of letters and association records related to the founding and leadership of the Ohio Woman Suffrage Association. Casement (1840-1928) was born in Painesville, Ohio, and graduated from Painesville Academy and Willoughby Female Seminary. Her father, Charles Casement, supported abolition and women's suffrage and encouraged Frances to be active in social causes. Frances Casement established the Painesville Equal Rights Association in 1883, and shortly after became involved in the Ohio Woman Suffrage Association, serving as its president from 1885 to 1888
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