Cop Definition and 43 Threads

I made a presentation where I derived, or at least attempted to derive, the formulae for the upper bounds of the efficiency/cop (cop = coefficient of performance) for a heat engine, work driven heat pump, and a heat driven heat pump with 3 thermal reservoirs, hot, warm, and cold. There are many...

Summary:: MCQ about COP of chiller The COP of a vapor compression chiller is characterized by its cooling capacity. At low cooling rates, the chiller COP is reduced by the effects of heat leaks to the environment. On the other hand, at high cooling rates, the chiller suffers from a) the high...

@Dale : “The COP of a heat pump and the efficiency of a heat engine both depend strongly on the temperatures of the hot and cold reservoirs. For this calculation you need to go back and check the sources for the temperatures corresponding to each of these numbers. You will find that the Stirling...

Can efficiency be larger than 100%? I have double checked the values of enthalpy of point 1,2,3 from R-22 tables. And I obtained enthalpy of point 4 from the work done given. Thank you.

I have tried to solve this with these equations: COP=T(H)/( T(H)-T(L) ) and COP = Q(H)/ ( Q(H)-Q(L) ) But since I need both Q and T in the same equation, I can't find anything to solve it.

This is a past exam Q, I don't have the attached pressure enthalpy diagram. Q = 120kW Cp = Refrigerant enthalpy = I've looked this up, for ammonia enthalpy = 35.06 kJ / mol T2 = 5 degrees C = (5 deg C) (1100 kPa/300 kPa) = 18.33 deg C +273.15 K = 291.48 K T1 = 2 degrees C = (2 deg C)(1100...

Homework Statement Homework Equations [/B][/B] 3. The Attempt at a Solution Here's my solution attempt: NOTE: Evolution 2 to 3 is really an isothermic process, but in the diagram shows as an politropic process. 4. Further Questions But it isn't giving me logical values of COP...

I still confuse about COP of refrigerator. When i read some journal, it is said that COP of VCRS can be greater than 1 (usually 2 - 4). But, why the COP other than VCRS usally lower than 1? like vortex tube, vapour absorption refrigeration system, etc. Actually, now i am doing a research about...

More specifically, does anybody know the sampling frequency of a mounted 360 degree cop radar? NOT a conical/directional hand-held radar gun.

Have always drooled over these awesome and mega priced babies until they started dissspearing. Cop says they are being replaced by sat phones which I thought were a nightmare to get a connection and crazy expensive. He would not discuss the performance. So awesome HF antenna versus sat phone...

Homework Statement Homework Equations N/A The Attempt at a Solution My question is a simple one: how is the above equation for COPref different to the COPref equations I've already encountered (such as COPref = Qc/Win = (h1-h4)/(h2-h1). Is the above just a different form of these? Or is the...

This problem was translated from Swedish, sorry for any grammatical errors present. 1. The problem A cop sets up a radar trap. A speeder passes the policeman and continues going at ##60km/h## even though the maximal allowed speed is ##50km/h##. The cop starts accelerating at ##5 m/s^2##...

Considering two thermal energy reservoirs, one at a higher temperature of TH compared to the other at TL, if we operate a reversible refrigeration cycle between the reservoirs then its coefficient of performance is given by, COPR,rev=TL/TH-TL This is the basically the maximum COP a...

Homework Statement Problem: A police car traveling at 80km/h is passed by speeder traveling at 145km/h. 3 seconds after the speeder passes, the police car starts accelerating at 2.5m/s2. How much time passes before the police overtakes the speeder (moving at a constant speed)? Variables...

I am trying to learn to calculate collisions on the center of percussion of a rod. Can you tell me how to find the moment of inertia? Suppose we have a rod of length 1m and mass M = 12 kg., we know that ##I = 12 * 1^2 / 3 = 4## , if a collision takes place at the CoP ( at 0.166666 m from the...

Hi experts... I'm new to this forum and want to know that why does COP(Coefficient of Performance) in heat pumps depend on time?

So if we start with question a) to calculate P = Q/t we can use that Q=m*c*ΔT so for for the 10 liters of water in the hot reservoir we get P=10*4186*25.8/1616=668 W. However it says the answer for a) is 667 W. Any idea why the difference? For question b) we have Vf = Pout / Pin where Pout =...

Dear all, I would to like to ask do anyone have any idea on how to increase the COP and SCP(Specific Cooling Power) of a silica gel absorption chiller? COP= Heat removed by evaporator/ Heat supplied to system( normally is the hot water supplied to the absorption bed) SCP= heat removed at...

Whenever I ask someone what an electromagnetic field is exactly, they say that science does how questions, not why questions (which doesn't really make sense in this context, maybe i worded my question differently). We say that there are four fundamental forces that create the universe we live...

The COP of a heat pump can be expressed as COP_{heating}=\frac{T_{hot}}{T_{hot}-{T_{cold}}} As higher is better, the value of this can be improved by reducing the temperature gap at which the system works. I'm just a little unsure about which temperatures are being talked about. The heat pump...

Hello everybody. I have trouble of proving the theoretical maximum of heat pump Coefficent of Performance. The thing I'm trying to calculate is for heat pump pumping heat from colder reservoir to the hotter reservoir: COP=Qh/W Qh - heat supplied to the hot reservoir(output) W - mechanical...

So I'm new here, and I apologize if I've posted in the wrong format/place/etc., but this is a makeup exam question, and I (think) I've finished it, but I want a second opinion on the correctness if you guys wouldn't mind. :smile: Homework Statement A speeding driver passes a hidden police...

Not sure if I am doing this correct and do not have answer available... A heat pump takes on 30,000BTU/hr of heat and uses 5030 watts. However its COP as an air conditioner is 2.19. How efficient is the pump and motor setup? I am assuming the following: Qh=30000 BTU/hr=11.79 hp WKin=5030...

Hi, I wonder how you calculate the "inverse COP" of a heat exchanger. Say a heat exchanger has a COP 4 at 0 degrees C. Under that condition the heat exchanger consumes 1kW, and deliver 4kW heat. So if you now turn it off, and instead heat one side and cool the other side with external heat...

Homework Statement I just want to know when do I use the formula for COP refrigerator vs COP Heat pump. If the heat is absorbing something then what formula do I use Homework Equations [b]3. The Attempt at a Solution [/b} Uh I just trying 2 figure out the concept so Idk how 2...

Homework Statement I am trying to work out the Cop of a heat pump in an experiment, I recorded the temperatures before and after the Condenser, but am unsure of how to calculate the work input to the condenser Homework Equations cop= heat gained at the condenser/ work input to the...

Homework Statement Compare a refrigerator set at +2 oC and a freezer set at -18 oC, both of which are operating in the room with temperature of +20 oC. What is relative amount of electric energy that will need to be used in both cases to cool a cup of water (250 ml) from room temperature to +5...

I need to know what distance a crown vic police car covers from 0-110mph It was a CHP in san diego and I'm pretty sure they drive the crown vic? Help

Did you guys hear about this ? Saw it on one of our news channels today. I generally am the first to support police and armed services, rule of law, etc, but this, IMO, is plain murder. The cop is a psycho - should never be allowed near a gun ever again.

Homework Statement The question is simply: A reversible refrigerator has a coefficient of performance equal to 13.8. What is its efficiency? Homework Equations COPrefrigerator = Tc/(Th - Tc) Efficiency = (Th - Tc) / Th The Attempt at a Solution I'm assuming I need to use these equations to...

Hi, has anybody worked with heat pumps? I'm recently confused about how the heat pump compressor operates. Does it have a fixed pressure or it actually adjust its pressure automatically to outdoor temperature variation? All my confusion originate from the following problem: Now we have a heat...

Hi All, I'm doing a study on effects of outside temperature on the energy efficiency of air-conditioning systems in computer server farms/data centers. It will be a simulated study so I cannot use the standard definition of COP; COP = heat removed / work At the same time I also want...

COP of a Refrigerant...Urgent Please Help! How do you find the COP ( Coefficient of Performance ) of a Refrigerant if you know the basic details of the refrigerant such as: Critical tempertaure Critical Pressure w Cp Also I am trying to calculate the VCC as well!? Any advice would be...

Homework Statement A motorcycle officer hidden at an intersection observes a car driven by an oblivious driver who ignores a stop sign and continues through the intersection at constant speed. The police officer takes off in pursuit 1.72 s after the car has passed the stop sign. She...

Homework Statement A state trooper sets up a radar trap. A speeder passes the trooper and continues going at a constant speed of 40 m/s. The instant the speeder passes the trooper, the trooper accelerates at 5.0 m/s/s for 10 seconds and then continues at a constant speed. How far will the...

Hi all, Why do they call a police officer a cop? (My first language is not English).

This is not a homework problem, I just want to know if this is possible. The cop is traveling in the opposite direction of me. Let's say I'm going 60mph and am speeding. He turns around, catches up to me, and clocks me going 15mph over the speed limit. Is this even possible? I found this...

Hi, I think I have confused myself over the COP of a refrigerator. I have refrigeration system and a certain set of values which enable me to plot a P-s diagram. The refrigerant is R-12. I also have another set of 4 results for varying evaporator pressures, and I have drawn all these...

Heard on the radio that the aircraft that crash landed at London airport crashed because of ice in the fuel (or that is the best guess) surly this is a cop out.

I was reading on the Clausius statement and heat pumps. Apparently, the COP (coefficient of performance) for heat pumps can be greater than unity (1), and it usually is for several systems (depending on the conditions). So the energy transfer due to work done on the system results in a greater...

Hi, I'm after some help because my intelligence doesn't stretch as far as you guys! I am being taken to court for speeding, the police officer has stated in her evidence that she saw me traveling at 80 mph, that at that time she was traveling at 70 mph. She then states that both she and I were...

A vessel containing 8.43 kg of water at 21.1C is put into a refrigerator. The 0.1655 hp motor runs for 9 min to cool the liquid to the refrigerator's low temperature 4C. What is the COP of the refrigerator? W=P(delta)t = 123.463Wx540s = 66670.02 J COP = Qc/W Please Help. Thank...

Hi! I am doing year eleven physics and love it, I am a teachers pet and all. Anyway, I have this theroy with my physics teacher, we came up with it together its really cool. So anyway, the expansion of the universe is accelerating, "defying gravity". Anyway, let's assume that it keeps...