Experimental and numerical study of the cold crucible melting process

The cold crucible, or induction skull melting process as is otherwise known, has the potential to produce high purity melts of a range of difficult to melt materials, including Ti–Al and Ti6Al4V alloys for Aerospace, Ti–Ta and other biocompatible materials for surgical implants, silicon for photovoltaic and electronic applications, etc. A water cooled AC coil surrounds the crucible causing induction currents to melt the alloy and partially suspend it against gravity away from water-cooled surfaces. Strong stirring takes place in the melt due to the induced electromagnetic Lorentz forces and very high temperatures are attainable under the right conditions (i.e., provided contact with water cooled walls is minimised). In a joint numerical and experimental research programme, various aspects of the design and operation of this process are investigated to increase our understanding of the physical mechanisms involved and to maximise process efficiency. A combination of FV and Spectral CFD techniques are used at Greenwich to tackle this problem numerically, with the experimental work taking place at Birmingham University. Results of this study, presented here, highlight the influence of turbulence and free surface behaviour on attained superheat and also discuss coil design variations and dual frequency options that may lead to winning crucible designs.

Experimental and numerical study of the cold crucible melting process

The cold crucible, or induction skull melting process as is otherwise known, has the potential to produce high purity melts of a range of difficult to melt materials, including Ti–Al and Ti6Al4V alloys for Aerospace, Ti–Ta and other biocompatible materials for surgical implants, silicon for photovoltaic and electronic applications, etc. A water cooled AC coil surrounds the crucible causing induction currents to melt the alloy and partially suspend it against gravity away from water-cooled surfaces. Strong stirring takes place in the melt due to the induced electromagnetic Lorentz forces and very high temperatures are attainable under the right conditions (i.e., provided contact with water cooled walls is minimised). In a joint numerical and experimental research programme, various aspects of the design and operation of this process are investigated to increase our understanding of the physical mechanisms involved and to maximise process efficiency. A combination of FV and Spectral CFD techniques are used at Greenwich to tackle this problem numerically, with the experimental work taking place at Birmingham University. Results of this study, presented here, highlight the influence of turbulence and free surface behaviour on attained superheat and also discuss coil design variations and dual frequency options that may lead to winning crucible designs.

"I’ll call you when we are ready" (One family’s experience of critical care and end of life decision making)

The purpose of this paper is to explore through narrative accounts one family's expérience of critical care, after the admission of a family member to an Intensive Care Unit (ICU) and their subséquent death five weeks later. Numerous studies support the need for effective communication and clear information to be given to the family. In this instance it was évident from their stories that there were numerous barriers to communication, including language and a lack of insight into the needs of the family. Many families do not understand the complexities of nursing care in an ICU so lack of communication by nursing staff was identified as uncaring behavior and encounters. Facilitating a family's proximity to a dying patient and encouraging them to participate in care helps to maintain some sensé of personal control. Despite a commitment to involving family members in care, which was enshrined in the Unit Philosophy, relatives were banished to the waiting room for hours. They experienced feelings of powerlessness and helplessness as they waited with other relatives for news following investigations or until 'the doctor had completed his rounds'. Explanations of "we must make 'the patient' comfortable" was no consolation for those who wished to be involved in care. The words "I'il call you when we are ready" became a mantra to the forgotten families who waited patiently for those with power to admit them to the ICU. Implications are this family felt they were left alone to cope with the traumatic expériences leading up to and surrounding the death. They felt mainly supported by the priest, who not only administered the last rites but provided spiritual support to the family and dealt sensitively with many issues. Paternalism in décision making when there is a moral obligation to ensure that discussions on end of life dilemmas are an inclusive process with families, doctors, nurses was not understood, therefore it caused conflict within the family over EOL décision making. The family felt that the opportunity to share expériences through telling and retelling their stories would enable them to reconfigure the past and create purpose in the future.