A model for the temperature dependence of the isobaric heat capacity of associated pure liquids C(p,m)(o)(T) is proposed. Taking the ideal gas as a reference state, the residual heat capacity is divided into nonspecific C(p) (res,ns) and associational C(p) (res,ass) contributions. Statistical mechanics is used to obtain C(p)(res,ass) by means of a two-state model. All the experimentally observed C(p,m)(o)(T) types of curves in the literature are qualitatively described from the combination of the ideal gas heat capacity C(p)(id)(T) and C(p)(res,ass)(T). The existence of C(p,m)(o)(T) curves with a maximum is predicted and experimentally observed, for the first time, through the measurement of C(p,m)(o)(T) for highly sterically hindered alcohols. A detailed quantitative analysis of C(p,m)(o)(T) for several series of substances (n-alkanes, linear and branched alcohols, and thiols) is made. All the basic features of C(p,m)(o)(T) at atmospheric and high pressures are successfully described, the model parameters being physically meaningful. In particular, the molecular association energies and the C(p)(res,ns) values from the proposed model are found to be in agreement with those obtained through quantum mechanical ab initio calculations and the Flory model, respectively. It is concluded that C(p,m)(o)(T) is governed by the association energy between molecules, their self-association capability and molecular size.
A simple association model for alcohol−alkane mixtures, based on the idea that only two energy states are
accessible to alcohol molecules in the pure and in the solution states, predicts complex temperature and
alcohol concentration dependences of the excess molar heat capacity,
. These predictions are tested
through the accurate measurement of pure component and solution heat capacities in the 278.15−338.15 K
temperature interval. These measurements were performed at low, equimolar, and high alcohol concentrations
for a linear alcohol (1-butanol) and a branched alcohol (3-methyl-3-pentanol) mixed with n-decane and with
toluene. The qualitative predictions from the two-state model are corroborated by the data. According to this
model, the very different
behaviors found for the different systems arise simply through the change in
hydrogen bonding Gibbs energy occurring on moving from the linear to the branched alcohol and in going
from the inert n-decane to the aromatic toluene.
Energy flexible buildings through smart demand-side management (DSM) or smart demand response (DR) using efficient energy storage, are currently one of the most promising options to deploy low-carbon technologies in the electricity networks without the need of reinforcing existing networks. Although, many ignore the potential, economic and energetic benefits these alternatives could hold for buildings, users and tariffs.In the study carried out a control system of demand management measures is analyzed, based on the use of the buildings' thermal mass as thermal storage (preheating, precooling and night ventilation). This demand management system is analyzed in five existing residential buildings in the so-called reference scenario (construction, user and current prices). Subsequently, comes the analysis of the optimal management strategy choice from the system, when facing changes in the housings' constructive characteristics and electric tariffs.The dynamism of the management system stands out from the results achieved, as well as the dependence of the possible strategy choices on the climate zones. In the reference situation, the maximum economic savings obtained after the implementation of the management system correspond to 3.2% for heating and 8.5% for cooling. In this same manner, when the buildings are previously rehabilitated, the savings can double even generating energy savings. Finally, it can be concluded that the low installation costs of these measures make them a winning solution, as long as the electric pricing and user behaviour allow the required flexibility.
The transformation of existing buildings into Near Zero Energy Buildings or even positive energy buildings remains a major challenge. In particular, historic buildings are an important cultural heritage that, in most cases, may be rehabilitated and reused for new purposes. However, achieving higher efficiencies in those buildings presents many difficulties, since there is a need to preserve aesthetic values and minimize impact on the buildings’ initial construction. In this work, a roadmap that allows rehabilitating a building from the eighteenth century is developed, turning it into a landmark building, to be used as a museum in the near future. The procedure is based on 3D models using REVIT software and detailed energy simulations supported by a cost-optimal methodology. The results reveal how conventional methodologies shown in the literature may improve the energy performance of the buildings during the heating regime, but performance may deteriorate during the cooling season. For that reason, the present study includes the design of a night ventilation system which allows not only solving this problem but also to reducing the cooling demands by more than 43% with little additional costs. In conclusion, historic buildings (which traditionally have a high thermal mass) have increased thermal storage potential by using the structures of the buildings themselves as well as passive cooling techniques.
The severity of extreme weather conditions brought on by climate change are conditioning quality of life, economic development, and well-being in today’s cities. Conventional measures have been shown to be insufficient for tackling climate change and must be supplemented with ecofriendly approaches. Hence, the scientific community’s endeavor to develop natural cooling techniques that lower energy consumption while delivering satisfactory comfort levels. For its simplicity and low cost, evaporative cooling has gained in popularity in recent years. The substantial cooling power to be drawn from evaporative mist cooling, makes it an attractive alternative to conventional systems. Research conducted to date on the technique has focused on producing cold air, whilst cooling the water involved has been neither assessed nor experimentally validated. No readily applicable simplified model for the system able to use operating parameters as input variables has been defined either. The present study consequently aimed to experimentally assess the cooling power of the evaporation of sprayed water and experimentally validate a simplified model to assess and design such systems. The findings confirmed the cooling power of the technique, with declines in water temperature of up to 6 °C, and with it the promise afforded by this natural air conditioning method. Finally, simplified model developed allows to evaluate this technique like a conventional system for producing fresh water.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.