What is Energy balance: Definition and 68 Discussions
In biology, energy homeostasis, or the homeostatic control of energy balance, is a biological process that involves the coordinated homeostatic regulation of food intake (energy inflow) and energy expenditure (energy outflow). The human brain, particularly the hypothalamus, plays a central role in regulating energy homeostasis and generating the sense of hunger by integrating a number of biochemical signals that transmit information about energy balance. Fifty percent of the energy from glucose metabolism is immediately converted to heat.Energy homeostasis is an important aspect of bioenergetics.
Let us assume a continuous flow of gas that can be ionized between the electrodes where an electric discharge is generated. According to the principle of conservation of energy, energy cannot be created or destroyed, but it can be transformed from one form to another with losses, e.g. in the...
McCabe - Thiele method is used to find minimum number of separation stages or theoretical plates for a given efficiency of separation in distillation for two - component mixture if components have similar enthalpy of vaporization.
If components have similar enthalpy of vaporization ,than on...
a) Two particles have energies E1 and E2, and momenta p1 and p2. Write down an expression for the invariant mass of this two-particle system. Leave your answer in terms of E1 and E2, and p1 and p2.
b) A typical photon (γ) in the Cosmic Microwave Background (CMB) has an energy of kBTCMB, where...
In the initial position the spring is previously compressed, then the block adds a force, and the spring is again deformed. I think the energy balance is incorrect; the potential energy of the spring is repeated.
a) λ = 4/3 by considering the energy balance as P moves from A (2a) to B (1/2a). The E.E. at A changes into a gain in gravitational potential energy + build up of E.E. at B since the spring compresses.
b) a = 5/3g by considering that the mass P is in dynamic equilibrium immediately after...
Why is energy balance for a control volume
dE/dt = dQ/dt-dW/dt-dm/dt(ΔH+ΔKE+ΔPE)
0 = dQ/dt-dW/dt-dm/dt(ΔH+ΔKE+ΔPE)
whereas for other systems it is
ΔE =Q-W-(ΔU+ΔKE+ΔPE)
0 = Q-W-(ΔU+ΔKE+ΔPE)
with enthalpy, h = u +pv, replaced by only the internal energy? How is the pv term accounted for...
I first found the height of the ball after it's passed the 45 degree angle by doing 4.12*sin(45) = 2.9133, and plugged in the rest of the variables (masses cancel)
.5(m)(vo^2) = (.5)(m)(vf^2) + mgh
(17.5^2)(.5) = (.5)(vf^2)(9.8*2.9133)
vf = 15.7845, however this is incorrect
I don't understand...
Hi, this problem should be very simple: I have a tank containing water. (going in and out). I want to write the differential equations to see what happen to the temperature and the level of the vessel if the flow of water is not constant.
the system should be:
$$A \frac {dl} {dt} = F_{in} -...
I am currently working on a project which requires a mass and energy balance on a fin/ fan heat exchanger. The problem I am running into is finding how to apply the fin efficiency to find out the amount of hea tbeing dissipated through the fins. The hot fluid is water and the cooling fluid is...
Hi guys,
I am currently working on my master thesis. I am supposed to make a dynamic model for a gas system and have some trouble setting up the energy balance. I am a noob when it comes to uploading pictures, so I don't have a figure for this, but let's consider a general control volume (CV)...
Homework Statement :[/B]Use the energy balance equations you wrote down for the ground layer, the atmospheric layer, and the above the atmosphere layer (space) in part (a) to show that the ground temperature Tg can be expressed in terms of the emission temperature TE as follows:
$$ T_g =...
Homework Statement
Use the data in the energy balance diagram for the Earth shown below to determine numerical values for α, a and e. Assess your results by comparing them to the commonly used approximations α = 0.3, a = 0 and e = 1. Show your calculations.
Homework Equations
Look at the the...
Homework Statement
In an industrial process, a tank containing 200 liters of water must be heated from a temperature of 293 K to 372 K at a constant pressure. There is a negligible change in the volume of the water. The water is stirred during this process to maintain a uniformly distributed...
I've learned that first thermodynamic law for some open system is in the form of:
where total change of system energy ##\frac{\partial E}{\partial \tau }## is equal to the transferred heat and work.
Total change of system energy ##\frac{\partial E}{\partial \tau }## is equal to the energy...
I am working on problem that has to deal with a jet ejector. For the life of me, I cannot figure out the E-Balance equation for it. Below is a cut away image of the ejector. The fluid is the same so using the ideal gas law I do not think should be included. Any help is greatly appreciated...
Homework Statement
As shown in Fig. P5.39, a system undergoing a power cycle develops a net power output of 1 MW while receiving energy by heat transfer from steam condensing from saturated vapor to saturated liquid at a pressure of 100 kPa. Energy is discharged from the cycle by heat transfer...
Question
A mass of 1.5 kg of air at 120 kPa and 24 C is contained in a piston-cylinder device. The air is compressed to a final pressure of 600 kPa. During the process heat is transferred from the air such that the temperature inside the cylinder remains constant. Calculate the work input...
Hello, PF!
I’m trying to model a real piping system, which has multiple inlets and one outlet, so I can’t use Bernoulli’s equation. Instead, I’m planning to use the generalized macroscopic energy balances as shown in BSL, which allow for any number of inlets and outlets. However, first I want...
Hi,
From the first law of thermodynamics it follows:
Cp * (δT/δt) = (δQ/δt)
where Cp = specific heat capacity, T = temperature, Q = heat, t = time
From this formula, you would derive that temperature keeps on increasing as long as dQ/dt > 0. But if you, for example, look at the idealized...
Hello,
I have a few questions regarding the osculating plane, which I understand to be the plane generated by the Principal unit tangent vector and principal unit normal vector (both are orthogonal), and the inertial Cartesian z-axis.
Ultimately, I plan to understand the geometric/kinematic...
Why is the rate of change of potential energy always same the rate of change of kinetic energy in a mass spring system?
Additiinally, How do we determine the rate of change of potential energy in such case?
Hi,
I am currently studying Thermodynamics and stumbled upon this equation and is slightly confused as to how this works. Hopefully someone can help me with the understanding.
According to this text here, if I am not wrong e can be h + ke + pe or u + ke + pe depending on where i am looking...
Hi PF!
For the longest time I thought an energy balance and the heat equation were identical procedures. However, recently I saw an example of a steady state, constant property, laminar flow of fluid between two flat surfaces where the top surface moves in the ##x## direction at ##V_1## and we...
Hey guys, I'm really stuck right now
1. Homework Statement
Habitable exoplanet:
Now we will include a convective heat flux (H), with H being proportional to the difference between the atmospheric and ground surface temperature, $$H=c_p(T_a-T_p)$$ with c = 1.2 Wm−2K−1. Calculate the temperature...
Hi all,
I'm having some trouble figuring out why entropy is used instead of enthalpy for an open system.
From what I understand, an open system uses entropy to calculate internal energy. Since the control volume is constant (i.e. Δv = 0), wouldn't using : h = u + PΔv effectively be h = u? So...
Homework Statement
Perform a one-dimensional energy balance for the heating of a fluid through a hot pipe in order to develop a differential equation that governs the variation of the mean temperature of the fluid along the length pipe. The pipe has an inner diameter D and length L; its walls...
Homework Statement
Water, initially saturated vapor at 4 bar, fills a closed, rigid container, The water is heated until its temperature is 400C. For the water, determine the heat transfer in KJ per kg of water .
Homework EquationsThe Attempt at a Solution
Assume potential and kinetic...
Hello,
I was reading an article, and I found something unfamiliar(sorry I am not into heat transfer a lot) :
For the energy balance of the fluid, I didn't understand the mCpθ where θ is the temperature and mCp(θ+dθ/dx θ) terms. I know that for a control volume, the energy balance for...
Homework Statement
For the reaction CH3OH(l) → CH4 (g)+ 1/2 O2 (g)[/B]
(a) Calculate ∆Ho298
(b) Calculate ∆Eo298
(c) Write an equation that would allow you to determine ∆H at 500°C and 1atm
Homework Equations
∆H=∆E+∆(PV)
∆H=Σ∆Hproducts-Σ∆Hreactants
The Attempt at a Solution
a)...
Good evening people of PF! I have recently encountered a problem from Himmelblau's Basic Principles and Calculations in Chem. E. which asks to set up an energy balance for a tank, and then non-dimensionalize the differential equation before solving it. It's not the most complex task, but it's...
Hi everyone.
I'm confused with the balance of energy in this situation (I'm comparing the mechanical energy, initially, at rest, at a height = h, and then, at the end, at height = 0). It doesn't seem to be fine, maybe I missed something.
I'd appreciate some help - Everything is in the .jpg...
Homework Statement
Lets say we have a series of balls and an eggs. All items have equal mass but are traveling at different velocities.
Thus they have differing kinetic energies.
Now, for each 'ball' object we have, we want to find an egg object with a similar kinetic energy. Let's say...
Hello PF! I have some questions regarding the accumulation term for the energy balance on a variable volume system. Suppose we have a tank storing a liquid substance. The tank has a moving boundary at the top, which can expand unlimitedly. The system has a mass input \dot{m}_1 and mass output...
Homework Statement
Pure iron sulfide (FeS2) is fed into an Herreshoff furnace at 25 °C. An 83% of excess air is also fed into the furnace at 25 °C. The solid product consists only of Fe2O3. The solid product reaches a temperature of 1832 °C, and the exhaust gases (8.7% SO2, 9.8% O2, 81.5% N2)...
Homework Statement
A block of mass m= 10kg rests on a horizontal table. The coefficient of friction between the block and the table is 0.05.
When hit by a bullet of mass 50 g moving with speed v, that gets embedded in it, the block moves and comes to stop after moving a distance of 2m on the...
The General Energy balance equation is:
∑ENin - ∑ENout + Egen = Est (in rate form - don't know how to put the dot above)
I know that Est is 0 when the system operates at Steady State Steady Flow (SSSF).
I have 2 formulas for ΔE in "Q-W = ΔE"
1) ΔE = ΔU + ΔKE + ΔPE
2) ΔE = m[h2 - h1...
Hello PF! I have a simple question on energy balances. Suppose you have an isothermal reactor where you want to have an exothermic reaction happening at 450 °C. The simplified energy balance for the reactor is Q = ΔH. Supposing ΔH = -150 kcal, then Q = -150 kcal. Does this mean that, a) in order...
Homework Statement
If we have a beta + deca: $$^{22}_{11}Na(3^+)\rightarrow ^{22}_{10}Ne(2^+)+ e^+ +\nu $$ with $t_{1/2}=2.6 years$, what is the energy balance at this decay, if you know that $^{22}_{10}Ne(2^+)$ is an excited state of $^{22}_{10}Ne$ with $1.25 MeV$ larger energy.
Homework...
Homework Statement
A train is traveling in the x direction at a speed of v. On the train, a passenger is playing darts and fires a dart in the y direction with a speed of Uy. The dart hits the target and stops abruptly. What is the difference in the mass of the dart as observed by a person on...
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Dear!
I have a problem with one, complex exercise. I’ve divided it into three parts just to simplify finding the answer. So let’s start.
The air is sucked from the atmosphere by a compressor. Atmospheric...
Two identical cars collide with equal and opposite velocity to each other. What happens to the energy? What happens to the momentum?
Answer: energy is converted into heat and momentum disappears. But what has that to do with force?
Hello PF! I have a very short question. We're currently doing enthalpy balances for chemical reactions in our Thermo class. We are using the simple enthalpy balance equation:
\Delta H_{\textrm{Reaction}}^0 = \sum \Delta H_{\textrm{Products}}^0 - \sum \Delta H_{\textrm{Reactants}}^0
My question...
Right, I'm sure this is bread and butter to a lot of you but I have just been introduced to the SFEE.
mgz+0.5mC^2+H +Q = mgz + 0.5mC^2 +H+W
Where Q is the heat transfer, W is work done and H is enthalpy. Where is it assumed that the heat energy is in the energy balance? If heat is added where...
I am currently looking facing a problem concerning a spring slider system.
The system consists of a electro engine that pulls on a spring with a constant velocity. The spring is attached to a block that sticks to the surface, but after a certain force is applied (by the spring) starts to slip...
Homework Statement
Using unsteady state energy balances, discuss why storing cold water will be better in a larger tank rather than a smaller one.
Assume the initial state where the tank is full.
The Attempt at a Solution
I've tried to make this an algebraic exercise where I created...
I'm trying to model a Transfer function for the response of the deviation in temperature of water coming out of the concentric tube heat exchanger in response to an input velocity of water function.
THE PROBLEM
I start the derivation with a couple equations in Seborg's Process Dynamics...
Hi everyone,
I am currently reviewing for a thermodynamics exam and have come across a difficult problem while studying. Here it is:
An insulated tank containing helium, a monatomic gas, at P1t = 1000kPa and T1 = 800K is connected to an initially evacuated insulated piston-cylinder device...
Several articles I've read describing one theory of how everything could have started from nothing. State that all the energy of nothing equals zero as gravity is negative energy. One of those articles was written by Stephen Hawkings. He also stated that quantum fluctations will always exist...
finding the "energy balance" of a hydroelectric power generator
I proposed a new hydroelectric energy idea to somebody and they asked me for a "energy balance". I know nothing about physics or anything relevant to calculating something like this. If somebody asked you for the energy balance of...