Evaluation of thermal comfort conditions in a classroom equipped with radiant cooling systems and subjected to uniform convective environment

The aim of this work is to evaluate numerically the human thermal response that 24 students and 1 teacher feel in a classroom equipped with radiant cooling systems and subjected to uniform convective environments, in lightly warm conditions. The evolution of thermal comfort conditions, using the PMV index, is made by the multi-nodal human thermal comfort model. In this numerical model, that works in transient or steady-state conditions and simulates simultaneously a group of persons, the three-dimensional body is divided in 24 cylindrical and 1 spherical elements. Each element is divided in four parts (core, muscle, fat and skin), sub-divided in several layers, and protected by several clothing layers. This numerical model is divided in six parts: human body thermal system, clothing thermal system, integral equations resolution system, thermoregulatory system, heat exchange between the body and the environment and thermal comfort evaluation. Seven different radiant systems are combined to three convective environments. In the radiant systems (1) no radiant system without warmed curtain, (2) no radiant system with warmed curtain, (3) radiant floors cooling system with warmed curtain, (4) radiant panels cooling system with warmed curtain, (5) radiant ceiling cooling system with warmed curtain, (6) radiant floor and panels cooling system with warmed curtain and (7) radiant ceiling and panels cooling system with warmed curtain are analysed, while in the convective environments (1) without air velocity field and with uniform air velocity field of (2) 0.2 m/s and (3) 0.6 m/s are also analysed. The internal air temperature and internal surfaces temperature are 28 degrees C, the radiant cooling surfaces temperature are 19 degrees C and the warmed internal curtains surfaces temperatures, subjected to direct solar radiation, are 40 degrees C. The numerical model calculates the Mean Radiant Temperature field, the human bodies' temperatures field and the thermal comfort level, for the 25 occupants, for the 21 analysed situations. Without uniform air velocity field, when only one individual radiant cooling system is used, the Predicted Percentage of Dissatisfied people is lowest when the radiant floor cooling system is applied and is highest when the radiant panel cooling system is applied. When are combined the radiant ceiling or the floor cooling systems with the radiant panel cooling system the Predicted Percentage of Dissatisfied people decreases. When the uniform air velocity increases the thermal comfort level, that the occupants are subjected, increases. When the radiant floor cooling system or the combination of radiant floor and panel cooling systems without uniform air velocity field is applied, the Category C is verified for some occupants. However, with a convective uniform air velocity field of 0.2 m/s the Category B is verified and with a convective uniform air velocity field of 0.6 m/s the Category A is verify for some occupants. In the last situation the Category C is verified, in general, for all occupants. (C) 2010 Elsevier Inc. All rights reserved

An Economic Model-Based Predictive Control to Manage the Users' Thermal Comfort in a Building

The goal of maintaining users' thermal comfort conditions in indoor environments may require complex regulation procedures and a proper energy management. This problem is being widely analyzed, since it has a direct effect on users' productivity. This paper presents an economic model-based predictive control (MPC) whose main strength is the use of the day-ahead price (DAP) in order to predict the energy consumption associated with the heating, ventilation and air conditioning (HVAC). In this way, the control system is able to maintain a high thermal comfort level by optimizing the use of the HVAC system and to reduce, at the same time, the energy consumption associated with it, as much as possible. Later, the performance of the proposed control system is tested through simulations with a non-linear model of a bioclimatic building room. Several simulation scenarios are considered as a test-bed. From the obtained results, it is possible to conclude that the control system has a good behavior in several situations, i.e., it can reach the users' thermal comfort for the analyzed situations, whereas the HVAC use is adjusted through the DAP; therefore, the energy savings associated with the HVAC is increased.Spanish Ministry of Science and Innovation [DPI2014-56364-C2-1-R]; EU-ERDF funds; Competitiveness and ERDF funds; Fundacion Iberdrola Espana; Portuguese Foundation for Science & Technology, through IDMEC, under LAETA [ID/EMS/50022/2013

A nongenomic mechanism for progesterone-mediated immunosuppression: Inhibition of K+ channels, Ca2+ signaling, and gene expression in T lymphocytes

The mechanism by which progesterone causes localized suppression of the immune response during pregnancy has remained elusive. Using human T lymphocytes and T cell lines, we show that progesterone, at concentrations found in the placenta, rapidly and reversibly blocks voltage-gated and calcium-activated K+ channels (KV and KCa, respectively), resulting in depolarization of the membrane potential. As a result, Ca2+ signaling and nuclear factor of activated T cells (NF-AT)-driven gene expression are inhibited. Progesterone acts distally to the initial steps of T cell receptor (TCR)-mediated signal transduction, since it blocks sustained Ca2+ signals after thapsigargin stimulation, as well as oscillatory Ca2+ signals, but not the Ca2+ transient after TCR stimulation. K+ channel blockade by progesterone is specific; other steroid hormones had little or no effect, although the progesterone antagonist RU 486 also blocked KV and KCa channels. Progesterone effectively blocked a broad spectrum of K+ channels, reducing both Kv1.3 and charybdotoxin-resistant components of KV current and KCa current in T cells, as well as blocking several cloned KV channels expressed in cell lines. Progesterone had little or no effect on a cloned voltage-gated Na+ channel, an inward rectifier K+ channel, or on lymphocyte Ca2+ and Cl- channels. We propose that direct inhibition of K+ channels in T cells by progesterone contributes to progesterone-induced immunosuppression

Assessing heat pumps as flexible load

In a future power system featuring significant renewable generation, the ability to manipulate domestic demand through the flexible operation of heat-led technologies such as heat pumps and micro-combined heat and power could be a critical factor in providing a secure and stable supply of electrical energy. Using a simulation-based approach, this study examined the linkage between the thermal characteristics of buildings and the scope for flexibility in the operating times of air source heat pumps. This was assessed against the resulting impact on the end-user’s comfort and convenience. A detached dwelling and flat were modelled in detail along with their heating system in order to determine the temporal shift achievable in the heat pump operating times for present-day and future dwellings. The simulation results indicated that the scope for shifting heat pump operating times in the existing building stock was limited, with time shifts of only 1–2 h achieved before there was a serious impact on the comfort of the occupant. However, if insulation levels were dramatically improved and substantial levels of thermal buffering were added into the heating system, sizable time shifts of up to 6 h were achievable without a significant impact on either space or hot water temperatures