No abstract

Purpose -The purpose of this paper is to introduce the solution to two-phase flow in CO 2 /brine system with salt precipitation by applying mixed hybrid finite element (MHFE) method to pressure equation and finite volume (FV) method to saturation equation. Mixed finite element method solves pressure and velocity in two subspaces while hybrid method is an extension of mixed method, where the Lagrange multiplier is added to the former in order to ensure the continuity from one element to the adjacent elements. The authors propose the modeling of salt precipitation using core flood experimental result and adapt to be applicable for numerical modeling. Design/methodology/approach -The governing equations are discretized using Mixed Hybrid Finite Element-Finite Volume (MHFE-FV) method. This method has the feature of localized conservation which is attractive for application on heterogeneous porous media. In addition to this, the salt precipitation effect is modeled using the data from core flood experiment (Ott et al., 2011). The random data are linearized to obtain the relationship between salt precipitate and CO 2 saturation and implemented to the algorithm for two-phase flow in CO 2 and brine system. Findings -The solution of MHFE-FV scheme has good agreement with the solution using implicit pressure and explicit saturation (IMPES) reported by Negara et al. (2011), with average error of 4.20 percent. Localized conservation is demonstrated in the case of randomized heterogeneous porous media where fingering effects are explicitly observed. Salt precipitation prediction using the proposed method is able to predict the decrement of porosity by 16.71 percent and permeability by 22.19 percent. This results in the decreased amount of CO 2 injected by 64.70 percent.Research limitations/implications -This paper presents the solution of two-phase flow in CO 2 brine system during CO 2 injection in saline aquifer using MHFE-FV method with the additional salt precipitation model obtained based on core flood experiment result. Practical implications -A methodology to predict the salt precipitation based on CO 2 saturation. Social implications -Contribution to green house gas reduction. Originality/value -The authors use MHFE-FV to solve hyperbolic PDE to obtain accurate results of CO 2 saturation, and subsequently use this to compute the salt precipitation.

The annual emission of CO 2 from human activities has exceeded the absorption abilities of nature. Carbon capture and geological storage is a solution that is able to combat the problem of excessive CO 2 release to the atmosphere, which endangers the lives of humans and all living things. Saline aquifer, which has a high permeability and storage capacity, has become a subject of interest as a CO 2 storage media. The flow of CO 2 into the aquifer initially occupied by saline water is the subject of study in this paper. Particularly, the effects of two significant parameters -capillary pressure and gravitational force have been considered. To solve the two phase flow equation, we have implemented the currently developed mixed and hybrid finite element method. The results show that capillary pressure enhance the flow of CO 2 whereas gravity force causes phase segregation with the less dense CO 2 flowing upward due to buoyancy forces.

Thermal comfort, which used to be a luxury in life has transformed into a necessity in modern lives. Tropical country such as Malaysia has hot and humid climate all year round. Much air conditioning is required in tropical countries to provide thermal comfort for indoor occupants. Fangers model is deterministic as it regards the heat fluxes across the boundary between humans and their thermal environment. Fangers model is adopted by ASRHAE Standard 55 in 1992 but it has over-predicted thermal preferences of those living in tropics. Malaysians who are used to hot and humid climates prefer warmer indoor temperature, as hypothesized in adaptive model. Adaptive model is said to predict thermal comfort more accurately than Fangers model as it relates the indoor comfortable temperature to outdoor air temperature. The objective of this research is to integrate the adaptive theories into Fangers model and to synthesize a new thermal comfort model which is expected to accurately predict thermal comfort in tropical countries. As the adaptive theory says that not all peoples thermal preferences are affected by thermal histories and contextual factors, the new model has proposed a broader operation range of PMV for air conditioner. The increment of PMV range from ±1.0 to ±1.17 for 80% satisfaction requirement is proved to applicable in Malaysia.

Abstract. This paper focused on supercritical CO2 injection into saline aquifer, in particular its capillarity's effects on the plume migration, reservoir pressure alteration and CO2 flux density. The numerical method used to solve the incompressible two-phase flow equations is based on the mimetic method, which conserves the mass and fluxes simultaneously. The investigation showed that exclusion of capillarity can greatly underestimate the CO2 plume migration and resulted in distinctive reservoir pressure distribution. It is found that capillarity showed no significant effect on the flux intensity of CO2.