An air conditioner with a power input of 1.2 kW is working as a refrigerator $(\beta=3)$ or as a heat pump $\left(\beta^{\prime}=4\right)$. It maintains an office at 20$^{\circ} \mathrm{C}$ year round that exchanges 0.5 kW per degree temperature difference with the atmosphere. Find the maximum and minimum outside temperatures for which this unit is sufficient.

A combination of a heat engine driving a heat pump takes waste energy at $50^{\circ} \mathrm{C}$ as a source $Q_{w 1}$ to the heat engine rejecting heat at $30^{\circ} \mathrm{C}$. The remainder, $Q_{w 2}$, goes into the heat pump that delivers a $Q_H$ at $150^{\circ} \mathrm{C}$. If the total waste energy is $5 \mathrm{MW}$, find the rate of energy delivered at the high temperature.

A steam turbine in a power plant receives 5 kg/s steam at 3000 kPa, 500$^{\circ} \mathrm{C}$. Twenty percent of the flow is extracted at 1000 kPa to a feedwater heater, and the remainder flows out at 200 kPa. Find the two exit temperatures and the turbine power output.

Give the missing property of P, T, v, and x for R-410a at. $r=-20^{\circ} \mathrm{C}$, P = 450 kPab. P = 300 kPa, v = 0.092 m3/kg

Consider the combination of a heat engine and a heat pump, as in earlier problem, with a low temperature of $400 \mathrm{~K}$. What should the high temperature be so that the heat engine is reversible? For that temperature, what is the COP for a reversible heat pump?

Determine the mass of methane gas stored in a 2-m3 tank at −30$^{\circ} \mathrm{C}$, 2 MPa. Estimate the percent error in the mass determination if the ideal gas model is used.

How does transient heat transfer differ from steady heat transfer? How does one-dimensional heat transfer differ from two-dimensional heat transfer?

How does the planning of fixed overhead costs differ from the planning of variable overhead costs?

The surface tension of water, a needed quantity in several of the following problems, is related to temperature according to the expression $\sigma$ = 0.1232 [1 − 0.00146 T] , where $\sigma$ is in N/m and T is in K. In the English system with σ given in lbf/ft and T in ? F, the surface tension may be calculated from$\sigma$ = (8.44 $\times$ 10−3) [1 = 0.00082 T].A square pan measuring 40 cm on a side and having a 2-cm-high lip on all sides has its surface maintained at 350 K. If this pan is situated in saturated steam at 372 K, how long will it be before condensate spills over the lip if the pan isa. horizontal?b. inclined at 10 degrees to the horizontal?c. inclined at 30 degrees to the horizontal?

Two parallel black disks are positioned coaxially with a distance of 0.25 m apart in a surrounding with a constant temperature of 300 K. The lower disk is 0.2 m is diameter and the upper disk is 0.4 m in diameter. If the lower disk is heated electrically at 100 W to maintain a uniform temperature of 500 K, determine the temperature of the upper disk.

Sylvan Creations designs, manufactures, and sells modern wood sculptures. Sandra Johnson is an artist for the company. Johnson has spent much of the past month working on the design of an intricate abstract piece. Jim Chase, product development manager, likes the design. However, he wants to make sure that the sculpture can be priced competitively. Ellen Cooper, Sylvan’s cost accountant, presents Chase with the following cost data for the expected production of 75 sculptures:

$$\begin{matrix} \text{Design cost} & \text{\$ 10.000}\\ \text{Direct materials} & \text{80.000}\\ \text{Direct manufacturing labor} & \text{27.500}\\ \text{Variable manufacturing overhead} & \text{10.000}\\ \text{Fixed manufacturing overhead} & \text{42.500}\\ \text{Fixed marketing costs} & \text{17.500}\\ \end{matrix}$$

1. Chase thinks that Sylvan Creations can successfully market each piece for $3.000. To earn the required return on capital, the company's target operating income per units is 20% of target price. Calculate the target full cost per unit of producing the 75 sculptures. Does the cost estimate Cooper developed meet Sylvan's requirements? Is value engineering needed? What is the total target operating income from the 75 sculptures? 2. Chase believes that competition will require Sylvan to reduce the price of the sculpture to$2.800. Rather than using the highest-grade wood available, Sylvan could use standard grade wood and lower the cost of direct materials by 25%. The redesign will require an additional $1.500 of design cost. Will this design change allow Sylvan to earn its total target operating income on the 75 sculptures? Is the cost of wood a locked-in cost? 3. If the price of the sculpture is$2.800, what is the total amount Sylvan can spend on direct materials for the 75 sculptures to earn the total target operating income calculated in requirement 1. What is the target cost per sculpture? 4. What challenges might managers at Sylvan Creations encounter in achieving the target cost and how might they overcome these challenges?

Thermal storage is made with a rock (granite) bed of 2 m3 that is heated to 400 K using solar energy. A heat engine receives a QH from the bed and rejects heat to the ambient at 290 K. The rock bed therefore cools down, and as it reaches 290 K the process stops. Find the energy the rock bed can give out. What is the heat engine efficiency at the beginning of the process and what is it at the end of the process?

A large stationary diesel engine produces 5 MW with a thermal efficiency of 40%. The exhaust gas, which we assume is air, flows out at 800 K and the temperature of the intake air is 290 K. How large a mass flow rate is that, assuming this is the only way we reject heat? Can the exhaust flow energy be used?

An ideal-gas Carnot cycle with air in a piston cylinder has a high temperature of $1200 \mathrm{~K}$ and a heat rejection at $400 \mathrm{~K}$. During the heat addition, the volume triples. Find the two specific heat transfers $(q)$ in the cycle and the overall cycle efficiency.