Utilities and energy-efficient design

What is the typical thermal efficiency range of a gas-turbine cogeneration plant with a heat recovery steam generator, as used to generate electricity on site?

What is a primary disadvantage of using electric power for heating in large-scale chemical plants compared to using fuels?

Fired heaters are typically used for process heating duties above what temperature, which is the approximate limit for high-pressure steam?

Estimate the annual cost of providing heat from a fired heater with a process duty of 4 MW. Assume the heater uses both radiant and convective sections, the price of natural gas is 3.20 dollars per MMBtu, and the plant operates for 8000 hours per year.

Which of the following is NOT listed as an advantage of using steam as a hot utility in chemical plants?

In a typical site steam system, what is the approximate pressure and corresponding condensing temperature for high-pressure (HP) steam?

When is a hot oil or specialized heat transfer fluid system most commonly used instead of multiple fired heaters?

What is the purpose of the 'blowdown' stream in a cooling water system?

What does the Coefficient of Performance (COP) of a refrigeration system represent?

A refrigeration cycle is needed to provide 1.2 MW of cooling duty at -5 C. The cycle rejects heat to cooling water at 40 C and has an efficiency of 80 percent of the Carnot cycle efficiency. The plant operates for 8000 hours per year, and electricity costs 0.06 dollars per kWh. What is the estimated annual operating cost?

What is a common problem to watch out for when setting up process simulation models, which represents a loss of heat or cooling potential?

What is the primary objective of a heat pump when used in the process industries?

In the mechanical vapor compression heat pump applied to a distillation column shown in Figure 3.12(b), what is used as the working fluid?

The calorific value of a waste gas is to be estimated. The combustion of Dichloroethane (DCE) is given by the reaction C2H4Cl2(g) + 2.5 O2(g) -> 2CO2(g) + H2O(g) + 2HCl(g). The standard heats of formation are: CO2 = -393.8 kJ/mol, H2O = -242.0 kJ/mol, HCl = -92.4 kJ/mol, and DCE = -130.0 kJ/mol. What is the heat of combustion for DCE?

What is the term for the set of techniques, developed by Bodo Linnhoff and collaborators, used for designing heat exchanger networks based on a thermodynamic break called a 'pinch'?

In a temperature-enthalpy (T-H) diagram for a two-stream heat exchanger problem, what is represented by the overlap of the hot and cold stream curves?

What is the thermodynamic significance of the pinch point in a heat exchanger network?

What is the primary consequence of designing a heat exchanger network that transfers heat across the pinch?

In the problem table method for pinch analysis, how are the interval temperatures (Tint) calculated from the actual stream temperatures (Tact) for a hot stream, given a minimum temperature difference (DTmin)?

In the heat cascade calculation of the problem table method, what does the final value at the bottom of the cascade represent after the minimum hot utility has been added at the top?

What is the key rule for matching heat exchanger streams immediately ABOVE the pinch to ensure maximum energy recovery?

What is the key rule for matching heat exchanger streams immediately BELOW the pinch to ensure maximum energy recovery?

When is stream splitting required in the design of a heat exchanger network at the pinch?

For simple networks, what is the minimum number of exchangers (Zmin), including heaters and coolers, according to Holmann's rule, where N' is the number of process and utility streams?

What defines a 'threshold problem' in pinch analysis?

If a process requires heating to a very high temperature necessitating a fired heater, what should be considered for the convective section of the heater to improve energy efficiency?

What is the primary challenge for energy management in batch and cyclic processes that is not present in steady-state processes?

In the batch preparation of an aqueous solution, 4545 kg of water is heated from 15 C to 80 C in a jacketed vessel. The jacket area is 27.9 m^2, the overall heat transfer coefficient is 285 W m^-2 K^-1, and the steam saturation temperature is 130 C. The specific heat capacity of water is 4.18 kJ kg^-1 K^-1. Estimate the heating time.

Which method of heat integration in batch processing is described as being the most thermally efficient, where streams are exchanged as they are pumped from one vessel to the next?

What is the typical efficiency of a fired process heater if both the radiant and convective sections are used for process heating?

In a process with multiple hot and cold streams, what is the practical minimum temperature difference (DTmin) in a heat exchanger usually between?

What does a temperature cross in a heat exchanger simulation indicate?

When recovering energy from high-pressure gas streams, what is often done to increase the power generated during expansion if the gas contains condensable components?

For a heat integration problem involving a hot stream cooled from 180 C to 60 C and a cold stream heated from 20 C to 135 C, with a DTmin of 10 C, what are the pinch temperatures for the hot and cold streams respectively?

Based on the problem described in Section 3.5, with two hot streams and two cold streams and a DTmin of 10 C, what are the minimum hot and cold utility requirements?

What is the primary function of demineralized water in a process plant?

What is the typical mains pressure at which compressed air is normally distributed in a plant for utility and instrument use?

In the context of energy recovery, why is it advisable to avoid mixing streams at different pressures?

What type of heat exchangers are commonly used in cryogenic processes to achieve true counter-current performance and very low-temperature approaches?

When is it economically justifiable to use process waste products as low-grade fuels?

What is the slope of a stream's line on a temperature-enthalpy (T-H) plot proportional to?

What is the defining feature of the heat exchange network design for maximum energy recovery, according to the summary rules?

In the general expression for the minimum number of exchangers for complex networks, Zmin = N' + L' - S, what does 'S' represent?

A simple heat-exchange system is being revamped for 50 percent higher capacity. In the base case, the cold side heat transfer coefficient for the steam heater E102 is 500 W/m^2K. Assuming the coefficient is proportional to the flow rate to the power of 0.8, what is the new cold-side coefficient in the revamp case?

What is the typical cooling range, the temperature difference between supply and return water, for most cooling towers?

What is the primary heat transfer mechanism in a cooling tower that allows water to be chilled?

For an ideal refrigeration cycle (a reverse Carnot cycle), how is the Coefficient of Performance (COP) calculated from the evaporator absolute temperature (Te) and condenser absolute temperature (Tc)?

In a steam system, what is the purpose of a back-pressure turbine?

A process has two hot streams (1 and 2) and two cold streams (3 and 4). Above the pinch, hot stream 1 (CP=3.0) and hot stream 2 (CP=1.0) are available. Cold stream 3 (CP=2.0) and cold stream 4 (CP=4.5) need heating. According to the CPh <= CPc rule, which match is NOT feasible immediately adjacent to the pinch?

Which utility fluid is commonly used as 'live steam' for applications like stripping vapor or sterilizing equipment?