Energy-efficiency specialists measure the heat Qh delivered by a heat pump and the corresponding electrical energy W needed to run the pump, and they compute the pump’s COP as the ratio Qh/W. They also measure the outdoor temperature, and they know that the pump produces hot water at Th = 52°C. The table below shows their results for Q and T. (a) Determine a quantity that, when you plot the COP against it, should give a straight line, (b) Make your plot, fit a straight line, and from it determine how the heat pump’s COP compares with the theoretical maximum COP.
Tc(°C) | −18 | −10 | −5 | 0 | 10 |
COP Qh/W | 2.7 | 3.2 | 3.6 | 3.7 | 4.7 |
Want to see the full answer?
Check out a sample textbook solutionChapter 19 Solutions
Essential University Physics: Volume 1 (3rd Edition)
Additional Science Textbook Solutions
Campbell Essential Biology (7th Edition)
Campbell Biology (11th Edition)
Microbiology: An Introduction
Chemistry: Structure and Properties (2nd Edition)
Human Physiology: An Integrated Approach (8th Edition)
Genetic Analysis: An Integrated Approach (3rd Edition)
- A gas expands from I to F in the figure below. The energy added to the gas by heat is 276 J when the gas goes from I to F along the diagonal path. A pressure-volume graph consists of points and line segments plotted on a coordinate plane, where the horizontal axis is V (liters)and the vertical axis is P (atm). Three points are plotted: point I at (2, 4) point A at (4, 4) point F at (4, 1) Line segments connect the three points to form a triangle. Arrows along the line segments point from I to A, from A to F, and from I to F. (a) What is the change in internal energy of the gas? J (b) How much energy must be added to the gas by heat along the indirect path IAF?arrow_forwardA heat pump is a heating system installed on some newer houses. It works by pumping heat from outside to inside. The efficiency of the heat pump is given by QH where W is the work done by an electric motor. The maximum theoretical efficiency of a heat pump is TH NHP maz TH – Tc 1. If the temperature outside is 44°F and the temperature inside is 65°F (these are the current temperatures outside and inside my apartment as I write this problem) what is the maximum possible efficiency of a heat pump. (Hint: You need to convert both temperatures to Kelvin first. Google can do this conversion for you.)arrow_forward(a) Considering the numbers of heads and tails, how many macrostates are there when five coins are tossed? (b) What is the total number of possible microstates in tossing five coins? (c) Find the number of microstates for each macrostate and be sure that the total agrees with your answer to part (b).arrow_forward
- Question-3: As advertisement revenue, billboards on vehicles can be used frequently. However, this fuel increases the cost. A block of 0.3m high, 0.9m wide and 0.9m long was placed on a taxi. Find the annual increase in fuel cost due to this billboard. Assume that the vehicle travels 60000 km per year, an average speed of 50 km / h and a total engine efficiency of 28%. Take the density, unit price and calorific value of gasoline as 0.75kg / L 5.5TL / L and 42000kJ / kg, respectively, and the density of the air as 1.25 kg / m3.arrow_forwardThe Table shown gives experimental values of the pressure P of a given mass of gas corresponding to various values of the volume V. According to thermodynamic principles, a relationship having the form PVk = C, where k and C are constants, should exist between the variables. Use the natural log (In) and linear regression to solve the following. 1) Find the value of k. a) 0.74 b) 0.86 c) 0.98 d) 1.33 2) Find the value of C. a) 812 b) 765 c) 880 d) 947 3) Estimate P when V = 100.0 in3 a) 18.9 b) 30.8 c) 24.7 d) 49.5 TABLE V(in3) 54.3 61.8 72.4 88.7 118.6 244.9 P(lb/in?) 61.2 49.5 36.6 28.4 19.2 20.1 Write only the letter corresponding to the correct answer.arrow_forwardThe average life expectancy in Japan is 81 years. What is this time in SI units?arrow_forward
- (a) Suppose that a person has an average heart rate of 72.0 beats/mm. How many beats does he or she have in 2.0 years? (b) In 2.00 years? (c) In 2.000 years?arrow_forwardThe heat supplied is 500 J. The heat loss to the environment is 160 J. Step 2 Calculation: Write the expression for the work output from the heat engine. W=Q1-Q2 Here, W is the useful workout, Q1 is the supplied heat, and Q2 is the heat loss. Substitute, all known values in the above expression. W=400 J-160 J=240 J Thus, the useful work is 240 J. What is the efficiency of the heat engine in the preceding problem at top? a) 32% b) 54% c) 68%. d) 75% e) 175%arrow_forwardA container is filled with an ideal diatomic gas to a pressure and volume of P₁ and V₁, respectively. The gas is then warmed in a two-step process that increases the pressure by a factor of four and the volume by a factor of five. Determine the amount of energy transferred to the gas by heat if the first step is carried out at constant volume and the second step at constant pressure. (Use any variable or symbol stated above as necessary.) Q = 63.5 The gas is in three different states. See if you can determine the pressure, volume, and temperature for each state and then the change in temperature during the two processes. Find expressions for the amount of heat supplied during isovolumetric and isobaric processes. Knowing the amounts of heat supplied during each process, how can you determine the total amount of heat supplied?arrow_forward
- An electrochemical engineer has manufactured a new type of fuel cell (a type of battery) which has to undergo testing to prove its duration: the time it takes to go from fully charged to completely uncharged, under a fixed nominal load. From the computational simulation models she has, the variance of the duration is o2 = 4 h² (hours squared) but she wants to estimate the mean duration time u. To achieve this she is determined to do the tests multiple times in independent but identical conditions. Can you find what is the smallest number of these tests that she has to do in order for her estimated mean duration to be within ±0.2 h tolerance of the true mean with 95% certainty?arrow_forwardWhat are the dimensions of the constant 1.26? Use the for- mula to estimate the mean free path of air at 20°C and 7 kPa. Would you consider air rarefied at this condition? Henri Darcy, a French engineer, proposed that the pressure drop Ap for flow at velocity V through a tube of length L could be correlated in the form AP - a LV If Darcy's formulation is consistent, what are the dimen- sions of the coefficient a?arrow_forwardThe formula for work in thermodynamics is given by PV=W. Suppose that at any pressure, P=h(V+Vo-1) where V is the volume and Vo is the initial volume. h and Vo are constants. If work is to be maximized, what is the correct expression of maximum work in terms of constants?arrow_forward
- Physics for Scientists and Engineers: Foundations...PhysicsISBN:9781133939146Author:Katz, Debora M.Publisher:Cengage LearningUniversity Physics Volume 1PhysicsISBN:9781938168277Author:William Moebs, Samuel J. Ling, Jeff SannyPublisher:OpenStax - Rice University