// Numbas version: finer_feedback_settings {"name": "Question 3 - Compressor", "extensions": [], "custom_part_types": [], "resources": [], "navigation": {"allowregen": true, "showfrontpage": false, "preventleave": false, "typeendtoleave": false}, "question_groups": [{"pickingStrategy": "all-ordered", "questions": [{"name": "Question 3 - Compressor", "tags": [], "metadata": {"description": "", "licence": "None specified"}, "statement": "

Air is compressed at steady state at a rate of {Q_in} m3/min from a pressure of {P_in} bar at {T_in} K to a pressure of 10 bar. The compressed air is discharged 3 m above the inlet.  During the process the air heats up to {T_out} K, whilst the compressor itself loses {Q_dot} kW of thermal energy to the surroundings. You may assume that the gas is ideal

", "advice": "", "rulesets": {}, "extensions": [], "builtin_constants": {"e": true, "pi,\u03c0": true, "i": true}, "constants": [], "variables": {"P_in": {"name": "P_in", "group": "Ungrouped variables", "definition": "random(0.5 .. 2#0.1)", "description": "

Inlet pressure

", "templateType": "randrange", "can_override": false}, "Q_in": {"name": "Q_in", "group": "Ungrouped variables", "definition": "random(5 .. 10#0.1)", "description": "

Inlet volumetric flow rate

", "templateType": "randrange", "can_override": false}, "Q_dot": {"name": "Q_dot", "group": "Ungrouped variables", "definition": "random(0.1 .. 2#0.1)", "description": "

Heat loss to the surroundings

", "templateType": "randrange", "can_override": false}, "m_dot": {"name": "m_dot", "group": "Ungrouped variables", "definition": "((Q_in/60)*(P_in*(10^5)))/((8.314/(28.97/1000))*T_in)", "description": "

Mass flow rate

", "templateType": "anything", "can_override": false}, "T_in": {"name": "T_in", "group": "Ungrouped variables", "definition": "300", "description": "

Inlet temperature

", "templateType": "number", "can_override": false}, "T_out": {"name": "T_out", "group": "Ungrouped variables", "definition": "random(391 .. 399#1)", "description": "", "templateType": "randrange", "can_override": false}, "h_out": {"name": "h_out", "group": "Ungrouped variables", "definition": "390.88 + ((T_out - 390)*((400.98-390.88)/(400-390)))", "description": "

Outlet specific enthalpy

", "templateType": "anything", "can_override": false}, "W_dot": {"name": "W_dot", "group": "Ungrouped variables", "definition": "-(Q_dot*1000) + (m_dot*(((300.19 - h_out)*1000) + (9.81*(0 - 3))))", "description": "

Work done

", "templateType": "anything", "can_override": false}}, "variablesTest": {"condition": "", "maxRuns": 100}, "ungrouped_variables": ["P_in", "Q_in", "Q_dot", "m_dot", "T_in", "T_out", "h_out", "W_dot"], "variable_groups": [], "functions": {}, "preamble": {"js": "", "css": ""}, "parts": [{"type": "numberentry", "useCustomName": true, "customName": "a)", "marks": "2", "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "prompt": "

Calculate the mass flow rate of air being compressed in kg/s. 

", "minValue": "m_dot*0.99", "maxValue": "m_dot*1.01", "correctAnswerFraction": false, "allowFractions": false, "mustBeReduced": false, "mustBeReducedPC": 0, "precisionType": "dp", "precision": "3", "precisionPartialCredit": 0, "precisionMessage": "You have not given your answer to the correct precision.", "strictPrecision": false, "showPrecisionHint": true, "notationStyles": ["plain", "en", "si-en"], "correctAnswerStyle": "plain"}, {"type": "numberentry", "useCustomName": false, "customName": "", "marks": "3", "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [{"variable": "m_dot", "part": "p0", "must_go_first": true}], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": "0", "exploreObjective": null, "prompt": "

Neglecting kinetic effects, determine the power required to perform the compression in W. 

", "minValue": "W_dot*1.01", "maxValue": "W_dot*0.99", "correctAnswerFraction": false, "allowFractions": false, "mustBeReduced": false, "mustBeReducedPC": 0, "precisionType": "dp", "precision": "1", "precisionPartialCredit": 0, "precisionMessage": "You have not given your answer to the correct precision.", "strictPrecision": false, "showPrecisionHint": true, "notationStyles": ["plain", "en", "si-en"], "correctAnswerStyle": "plain"}], "partsMode": "all", "maxMarks": 0, "objectives": [], "penalties": [], "objectiveVisibility": "always", "penaltyVisibility": "always", "type": "question", "contributors": [{"name": "Jonathan McDonough", "profile_url": "https://numbas.mathcentre.ac.uk/accounts/profile/12473/"}]}]}], "contributors": [{"name": "Jonathan McDonough", "profile_url": "https://numbas.mathcentre.ac.uk/accounts/profile/12473/"}]}