I recently set an in-class assignment for my second year class to whom I give a short course on Heat Transfer. The students were given half an hour to answer the following question:
The U-value, or heat transfer coefficient, is used frequently in everyday life, especially in the areas of energy efficiency and energy rating. A family member asks you to explain this parameter. In the space below, write out the explanation you would give to him or her.
Below are four selected answers, chosen pretty much at random. They are reproduced exactly as written so the typos are not mine.
I am not showing these for a cheap laugh at the expense of students and should point out that receiving answers like this is a regular occurrence and no longer makes me stop in my tracks.
Overall heat transfer coefficient, say your using a system and you need to record how long it takes this system to heat up, The amount of time it takes This system to Heat up is used to calculate the overall heat transfer coefficient is the Resistance of the heat transfer. Recently In our engineering labs, we had to do an experiment to Record the a series of values over time and from these values and our experimental graph we were given an equation to calculate the heat transfer coefficient. However the experiment had been set up wrong and Recorded the cooling down of the liquid Rather than the Heating up. It is used in many different formulas.
The U-value is an important parameter and can be used in lots of calculations of Resistance. It can also be used alongside area to calculate heat transfer in a bioreactor with a jacket, so calculating heat in the bioreactor and the heat of the jacket. If you want to measure the resistance of two separate identies in the same system you put 1 over h either of them and add them together. Because we are able to find out this U value it allows us to make the most of a system allowing us to sustain energy more effectively which is important in all areas of industry and economy. It is important in the household and in industry to have a good energy rating and to sustain michenery to last longer.
The U-value describes the transfer of heat. It described how efficient something is in transferring heat. In the home there are many applications of heat transfer. For example kettles or toasters. Kettles take in energy, in the form of electricity & use it to boil water. The energy is converted from electrical energy to heat energy which crosses the barrier into the water & heats up. It is necessary to have a kettle which transfers the heat efficiently. Otherwise too much electricity would be used, thus wasting money. So kettles have an energy rating which tells us how efficient it is. This efficiency is expressed by a value of U. Every electrical object is given a U-value. The more energy efficient (i.e., best U-value) the more expensive the ulensil is. However, an energy efficient object will save you money on using less electricity.
The U-value is a measure of how quickly a system can cool down or heat up. It the overall heat transfer coefficient. The term coefficient means that it is used in a formula containing variables. The U-value can be determined by the following equation: U=(1/h1+1/h2+….1/hn}^-1. This means putting one over each heat transfer coefficient, adding them, then raising the total to a power of -1. The U-value is useful for determining how insulated a house or appliance is. Its units are W/m^2K).
In internet parlance, wtf ! How can a second year university student be so incoherent? Am I just seeing a small, unrepresentative sample of third level students or is this indicative of a wide-ranging problem? If the latter is the case, and if it has been going on for a significant period, those of us who have not been shouting from the rooftops about it should be deeply ashamed.
I may be overreacting here and getting cranky, intolerant and unrealistic in my expectations of students. However, to put my mind at ease I would like to see a forensic assessment of quality and standards in Universities, benchmarked against the best international standards. That means panels of experts, rather like a fraud squad, getting down and dirty with exam papers, lab reports, essay assignments, the lot. There are many, I’m sure , who will say that we already have such a system in place via the extern examiner system. In my experience, this is not rigorous enough.
Update: Thanks to all of those who have replied with some very long and detailed replies. They are appreciated as are all other comments – good and bad – on my other posts. I don’t have time to follow these up as much as I should and apologies for that. On this specific post, it is clear that people are seeing some horrific stuff out there.