Less Is More Pearson, Andy
ASHRAE journal,
09/2022, Letnik:
64, Številka:
9
Journal Article
Recenzirano
The Herrick Compressor Conference at Purdue University has been held every second year since 1972 and at the meeting in July this year it was clear that there is as much to learn as there ever was, ...if not more. To celebrate the 50th anniversary the plenary address on the last day of the conference was in the form of a panel discussion, moderated by the conference chair, Professor Eckhard Groll, and with three representatives from some of the largest and most successful compressor manufacturing companies in the world.
Whisky: Water of Life Pearson, Andy
ASHRAE journal,
07/2017, Letnik:
59, Številka:
7
Journal Article
Recenzirano
I have to confess I am a bit of a failure as a stereotype of the Scottish male. I can't play the bagpipes, I don't do golf, and I have never been to a professional soccer game in my life, despite ...being born and bred in a city famous for the intense rivalry of its two teams--on a par with Madrid, Manchester, or Milan. Until recently I was not a whisky drinker either, but getting older brings some compensations, including developing a taste for olives and fine whisky, although not together.
The systemic complexity of sustainable development imposes a major cognitive challenge to students' learning. Faculty can explore new approaches in the classroom to teach the topic successfully, ...including the use of technology. We conducted an experiment to compare the effectiveness of a simulation vis-à-vis a case-based method to teach sustainable development. We found that both pedagogical methods are effective for teaching this concept, although our results support the idea that simulations are slightly more effective than case studies, particularly to teach its multidimensional and inter-temporal nature. Therefore, our findings suggest the use of both simulations and case studies as pedagogical tools to convey the main ideas associated with sustainable development.
No Excuses Pearson, Andy
ASHRAE journal,
07/2016, Letnik:
58, Številka:
7
Journal Article
Recenzirano
Pearson talks about the practice of measuring chiller capacity in tons that seems to encourage vagueness about actual quantity. A ton of cooling is actually a very precise amount of heat transfer, ...equivalent to the removal of 3,517 Joules per second. If the chiller's cooling capacity is being measured in tons, then there seems little point in being any more precise about the electrical use.
Studies on COVID-19 usually focus on health system responses to decrease the rate of COVID-19 infection and death, but patients with other diseases also require access to health services during the ...pandemic. This paper describes the structures and processes by which the Costa Rican Social Security Fund (CCSS) changed in response to the COVID-19 pandemic, which helped to sustain essential health services (EHSs). We conducted a desk review of the local literature and semistructured qualitative interviews with key informants from the CCSS. We found that the CCSS implemented changes in structure, such as creating a specialised COVID-19 centre and hiring additional interim health workers. The CCSS also implemented changes in processes, including leveraging its integrated network to optimise its resources and support alternative care modalities. These changes generated changes in outputs and outcomes that helped sustain EHSs for non-COVID-19 patients. These interventions were possible primarily due to Costa Rica’s underlying health system, particularly its integrated nature with a single institution in charge of healthcare provision financed through mandatory health insurance, a unique digital medical record system and a contingency fund.
Great Balls of Fire Pearson, Andy
ASHRAE journal,
06/2024, Letnik:
66, Številka:
6
Journal Article
Recenzirano
Pearson talks about Dr S Forbes Pearson and his inventions. One of the most widely commercialized ideas led by Forbes, among others, was the use of zeotropic mixtures in refrigeration systems. This ...work in the 1980s was done in parallel with several other researchers, particularly in America. Searching for a substitute for R-502 in the mid-1980s, Forbes decided to add some propane to R-22 in order to improve oil return in the same way and set up his own "great balls of fire" to establish how much propane would make the mixture flammable. Forbes believed firmly in sharing information, reckoning that he always gained more than he gave in these exchanges.
Pearson talks about French scientist Sadi Carnot who first published the explanation of the relationship between heat and work, "thermodynamics."Carnot is world-famous but little of his life story is ...known, and he is often incorrectly characterized as a loner who developed his theory in isolation from the scientific community, not recognized in his lifetime. He befriended two chemists, Nicolas Clement and Charles Bernard Desormes, both about twenty years older than Carnot. At that time they were working on a method to determine the ratio of specific heats, known as the adiabatic index or Laplace Coefficient. Apart from his scientific and engineering studies from the age of 22 onward, Carnot was widely read and enjoyed physical sports as well as being an accomplished musician, playing piano and violin. A measure of his character can be gained from the aphorisms jotted in his notebooks, which give the impression of a modest man, not keen to take center stage but happy to share a joke with friends.
Pearson shares his preferred defrost method. His preferred defrost method, when it is possible, is to swap the evaporator and condenser of the refrigeration plant and run it as a heat pump for a ...short time. The plant is fitted with a four-port ball valve, located in the discharge line between the oil separator and the condenser with the wet return line from the evaporator to the low side receiver passing through it. By rotating the ball in this valve through 90°, the discharge gas can be directed in the reverse direction up the wet return line from the compressor to the evaporator. The gas gives up its latent heat in the evaporator, turning to liquid which flows in reverse from the evaporator to the condenser, passing through an expansion device on the way and then evaporating in the condenser at low pressure. The evaporated gas passes back through the ball valve and into the low side receiver, and then on to the compressor suction.
The most common defrost system in industrial systems is to use "hot" gas. But even within the hot gas camp, there are massive differences of opinion that put even the Packers vs. Bears debate in the ...shade. Some people are so one-sided in this regard that they don't even realize that an alternative exists. To understand this, it is necessary to start with the basic physics behind hot gas defrosting. The basic defrost process seals off an air cooler from the suction side of the refrigeration plant and opens it up to the discharge side, allowing higher pressure gas to flow into the tubes of the evaporator. This gas gives up its latent heat and condenses to liquid, adding the heat to the tubes and fi ns of the evaporator. This warms them up and, provided the gas pressure is high enough, they will get hot enough to melt any frost that has formed, allowing the melt water to flow down the drain.
Nipping at Your Nose Pearson, Andy
ASHRAE journal,
03/2024, Letnik:
66, Številka:
3
Journal Article
Recenzirano
Pearson discusses the defrosting cycle in refrigeration systems. At face value, frost buildup on an air cooler in a cold store is a bad thing, causing an insulating effect on the surface of the heat ...exchanger and restricting airflow. However, in the very early stages of frost buildup on a clean metal surface, the ice crystals form spiky fingers called "dendrites," which have the initial effect of increasing the effective surface area on the air side and improving the heat transfer performance. In an ideal world, the air cooler would get slightly frosted and stay that way. Unfortunately this is a passing phase and soon the performance degradation is significant enough to require action.
